we are aliens – a guide for educators

EUGENE SCIENCE CENTER2300 Leo Harris Parkway, Eugene, OR 97401. [email protected], 541-682-7888

We Are Aliens – A Guide for Educators

Prepared by Haley Sharp, Eugene Science Center Planetarium Director, [email protected] About the Planetarium Show We Are Aliens invites your students to explore how our understanding of life on Earth guides the hunt for alien life elsewhere in the universe. We visit Mars, Europa and distant exoplanets to help answer the ultimate question... are we alone? Explore what life needs to thrive and how astronomers use clever techniques to find planets around distant stars in this immersive program that perfectly balances science, education, and entertainment. Next Generation Science Standards

We Are Aliens explores topics in each of the four disciplinary core ideas as outlined in the Next Generation Science Standards: physical sciences; life sciences; earth and space sciences; and engineering, technology, and applications of science. From a thorough investigation of the incredible diversity of lifeforms found on Earth, to imagining space missions that can hunt for alien life in our solar system and beyond, there are many ways to connect this planetarium program to your current science lessons. Some relevant standards are listed below: K-LS1-1 Use observations to describe patterns of what plants and animals need to survive.

1-ESS1-1 Use observations of the sun, moon, and stars to describe patterns that can be predicted.

2-LS4-1 Make observations of planets and animals to compare the diversity of life in different habitats.

2-ESS2-3 Obtain information to identify where water is found on Earth and that it can be solid or liquid.

3-LS4-3 Construct an argument with evidence that in a particular habitat some organisms can survive well, some survive less well, and some cannot survive at all.

3-LS3-2 Use evidence to support the explanation that traits can be influenced by the environment.

4-PS4-1 Develop a model of waves to describe patterns in terms of amplitude and wavelength.

5-PS3-1 Use models to describe that energy in animals’ food was once energy from the sun.

5-ESS2-1 Describe and graph the amounts and percentages of water and fresh water in various reservoirs to provide evidence about the distribution of water on Earth.

MS-PS2-4 Construct and present arguments using evidence to support the claim that gravitational interactions are attractive and depend on the masses of interacting objects.

MS-LS4-2 Apply scientific ideas to construct an explanation for the anatomical similarities and differences among modern organisms and between modern and fossil organisms to infer evolutionary relationships.

For more information on Oregon’s Science Standards, visit http://www.ode.state.or.us/search/page/?id=1577


Before Your Visit • Begin by assessing what your students already know about the search for life beyond Earth.

Specifically, invite them to share what they have heard on their own. For example: o What does Earth have that makes it such a haven for life? o Where else in our solar system could we look for life? How are these places similar to

and/or different from the Earth. o Is the Sun the only star that has planets? Are planets common in the universe? o Poll your students to see how many of them believe in alien life.

Remind your students that some of these may be open-ended questions, like many great questions in science! While scientists are looking for signs of life beyond Earth, we haven’t found any yet. Activities For Before or After Your Visit • In any astronomy unit, one of the most challenging concepts to convey is just how big and

empty space truly is. This activity will allow your students to work together to create a scale model of the Earth, Earth’s moon, and Mars using balloons. Students will first make their models based on what they think is the correct scale before you show them the accurate model. Use this activity to explore as a group why it is so challenging to travel to Mars and beyond. Full activity description: https://marsed.asu.edu/sites/default/files/stem_resources/Earth_Moon_Mars_ Balloons _K-4_Lesson_8_2013.pdf

• In space exploration, robotic rovers are sent to destinations like Mars to test landing procedures and explore these locations before humans can safely travel there. But studying the Martian environment through the “eyes” of a robotic rover is no easy task. In this activity, students will bring an item from home in a paper bag. Then, these bags of items will be randomly distributed to students and they will have to use their senses to make inferences about the nature of the hidden item based on their indirect observations. Full activity description: http://www.nasa.gov/audience/foreducators/topnav/materials/listbytype/ Whats_Hidden_Inside_Activity.html

• This activity will demonstrate that when scientists look for life on Mars, or elsewhere in the universe, the signs of life are not always easy to determine. Begin by discussing with your students how they think life is defined and then conduct a simple experiment looking for signs of life in three different “soil” samples. Following the experiment, you may need to reassess how living things vs. non-living things are defined. Full activity description: www.lpi.usra.edu/education/explore/LifeOnMars/activities/searchingForLife/

• When scientists discover exoplanets – planets orbiting stars other than our sun – the first thing they will do is try to determine if that exoplanet is orbiting in its stars’ “habitable” zone where it is not too hot and not too cold, but just the right temperature for liquid water. This video is an example of a demonstration you can do in class with your students exploring what the habitable zone is using the innermost planets or our solar system as an example. Full activity description: https://nightsky.jpl.nasa.gov/download-view.cfm?Doc_ID=311


Useful Websites • NASA’s exoplanet site: https://exoplanets.nasa.gov/

o New exoplanet discoveries are announced all the time. While this is exciting from a scientist’s perspective, as an educator it can be frustrating to have out-of-date information. NASA’s exoplanet archive is the go-to resource for the current number of confirmed exoplanets in our galaxy.

• NASA’s Mars exploration site: http://mars.nasa.gov/ o This is a great collection of all things Mars. Highlights include a history of Mars

missions, the latest press releases of new discoveries made about the red planet, and a wonderful collection of multimedia resources to share with your students.

• NASA’s Space Place: http://spaceplace.nasa.gov/ o NASA’s Space Place website is a wonderful resource for general space information.

This site includes kid-friendly educational games, hands-on activities, and lots of beautiful space images to help visualize the cosmos.

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WeAreAliens!–Classroomactivity1(Biology)

Istherelifeinthere?

Background:

AlllifeformsonEartharebasedonorganicbiochemistry.Thisactivityrequiresstudentsto

analyseanunknownsoilsample(justrecoveredfromaspacemissiontoanotherplanet!)and

lookforsignsofcarbohydrates,lipidsandproteinsaspossibleindicatorsforlife.Theresultsfrom

thepracticalinvestigationmirrorthoseoftheVikingmissionsthatfirstanalysedthesurfaceof

Marsinthe1970’s.

TheactivitycoversavarietyofcurriculumareasandcanbeusedacrossKS3,KS4,andKS5with

modificationanddifferentiation.

Curriculumareascovered:

• Cellbiology

• Foodtests–biochemicaltestsforprotein,fatandcarbohydrates(starchandreducingsugar)

• Practicalskills–handlinglaboratoryglasswareandreagents,makingobservations,preparing

slides,usingalightmicroscope

• HowScienceWorks–formulationofatheory,needforreliability,peerreview

Equipmentlist:

• ThreecontainerslabelledA,BandC(sizeoptional)

• Soilsamplesineachcontainer.Eachsampletovaryintermsofitscontent–examplebelow:

Theexactquantitiesofeachsubstanceinthecontainersarenotcrucial–thetestsaresensitive

enoughtopickupsmallamountsofeachorganicmolecule.Asaroughguide,about4parts

sandto1part‘extraingredients’isusuallysufficient.

• Testtubes

• Spatulas

• Waterbaths

• Pipettes

• Handlenses

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• Sildes&coverslips

• Microscopes

Reagents:

• Benedict’ssolution

• BiuretA&BiuretBsolutions

• Ethanol

• PotassiumIodidesolution

Method:

Visualinspection:

1. Askstudentstotakeasmallamountofeach‘soil’typeandplaceonseparatepiecesofpaper

2. Studentsobservewiththenakedeyeandrecordanyobviousdifferencesbetweeneachsoil

typeontheresultssheet

3. Asmallquantityofeachsoilsampleisthenplacedintoadimpletile.Addafewdropsof

warmwater(enoughtocoverthesoil)toeachsample.Observecarefullyoverthenextfive

minutesandrecordobservationsontheresultssheet

Lookingforcells(yeast):

Placeasmallamountofeachhydratedsoilsample(useapipette)onseparateslidesandobserve

atlow,mediumandhighpowermagnification.Recordyourobservationsontheresultssheet

Starchtest:

1. Takeasmallamountofeach‘soil’typeandplaceinseparatetesttubes

2. Addapprox5cm3ofwatertothetesttubeandshake

3. Allowtimeforthesoiltoformasedimentatthebottomofthetube

4. Addafewdropsofiodinesolutiontothetesttubeandobserveanycolour

change.Ablackcolourindicatesthepresenceofstarch

5. Recordresultsontheresultssheet

Reducingsugartest:




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4. Addapprox5cm3ofBenedict’ssolutiontothetesttubeandplaceinahotwater

bathforfiveminutes.Abrickredcolourindicatesthepresenceoflargequantities

ofreducingsugars.Yellow/Green/Orangecoloursindicatesmallerquantities.

5. Recordresultsontheresultssheet

Proteintest:




4. AddafewdropsofBiuretAsolutiontothetesttubeandthenaddafewdropsof

BiuretBsolution.Observeanycolourchange.Apurplecolourindicatesthe

presenceofprotein

Lipidtest:

1. Addapprox5cm3ofethanoltothetesttubeandshake


3. Addafewdropsofwatertothetesttube.Observeanycolourchange.Amilky

whitecolourindicatesthepresenceofalipid.

TherapideffervescenceseeninBistypicalofashortbutunsustainedchemicalreaction–

reminiscentofthelabelledreleaseexperimentperformedbytheVikingprobesonMars

(seebelow).ThecontinualreleaseofgasinCillustratesanimportantfeatureoflife–that

ofsustainability.

Discussion:

Afterstudentshavecompletedthepracticalandfilledintheirresultssheets,two

studentsshouldactasa‘peerreviewpanel’andcollateresultsfromdifferentgroupsand

displayontheboard.Discussionfollowsontheoverallresultsoftheclass,reasonsfor

anydisagreement,contamination,anomalies,etc.DiscussionleadsintotheVikingLander

missionsandtheparallelsbetweenthisinvestigationandthosecarriedoutonthe

surfaceofMars.ThemainlinkistheideaofsandsampleBgivingoffagreatdealofgas–

butitbeingentirelyduetochemical,andnotbiological,reactions.

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SoilA SoilB SoilC

Visual

inspection

Responseto

hydration

Testforstarch

Testforsugar

Testforprotein

Testforfat

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Backgroundinformation-Mars

Marsisbyfarthemoststudiedplanetinoursolarsystem.Ithasnotablesurfacesimilaritieswith

Earthincludingvolcanoes,mountains,valleys,desertsandpolaricecaps,althoughitis

approximatelyonlyhalfthesizeoftheEarth.Marscurrentlyhoststhreeactivespaceprobesin

orbit(MarsOdyssey(NASA),MarsExpress(ESA)andtheMarsReconnaissanceOrbiter(NASA)).Italsohastwoexplorationroversonthesurface(SpiritandOpportunity(NASA))plusahostofinertprobesfromthepast–includingtheBritishBeagle2probeandNASA’sPhoenixprobe,whichrecentlycompleteditsmissiontoresearchthehistoryofwaterontheplanet.

Thedatagatheredthusfarhasshownthat:

• Thesurfaceiscomposedoffineiron(III)oxide–givingMarsitsrustredcolouration

• Thereisevidenceofgeologicalactivityandplatetectonics(asevidencedbyVallesMarineris,

OlympusMonsandpaleomagnetismofminerals),butthisseemstohavestoppedalong

timeago.ThisispossiblyduetothefactthatMarsismuchsmallerthanEarthandsolost

heatmorerapidly,leadingtocoolingandsolidificationofthecore.

• Marsappearstohavelostitsmagneticfieldearlyoninitshistory,meaningthattheSolar

Windhasstrippedawaymuchofitsatmosphere.Whatatmosphereremainsisverythinand

iscomprisedmainlyofcarbondioxide(95%)withsmallerquantitiesofnitrogen(3%),argon

(1.6%)andtraceamountsofoxygen.

• Alackofozoneintheatmospheremeansthatthesurfaceisirradiatedwithlargequantities

ofUVradiation–meaningthatorganicmoleculesonthesurfacewouldbequicklybroken

down

• Thethinatmospheremeansthatairpressureisverylowrangingfrom0.03KPa(summitof

OlympusMons)to1.155KPa(depthsofHellasPlanitia).

• MethanehasbeenfoundintheMartianatmospherewithaconcentrationofabout30ppb

byvolume.Sincemethaneisanunstablegasthatisbrokendownbyultravioletradiation,

typicallylastingabout340yearsintheMartianatmosphere,itspresencewouldindicatea

currentorrecentsourceofthegasontheplanet.

• SignificantamountsofwatericehavebeenfoundatthepolesofMarsandhavealsobe

foundunderthesurfaceinotherlocations.NASAhasestimatedthatthereissufficientwater

iceatthepolesalonetofloodtheplanettoadepthof11metresifmelted.Surfacefeatures

ofMarsindicatethatinthepastwatermayhaveexistedinliquidform.

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VikingInvaders…

Itisnowmorethan30yearssincethefirstsearchforlifetookplaceon

anotherplanet–Mars.Inthemid1970’sNASA’stwoVikinglandersconductedbiologyexperimentslookingforbiosignatures.Theseexperimentsincluded:

GasChromatograph—MassSpectrometer

Designedtoseparate,identifyandquantifyalargenumberofdifferent

chemicals.Particularinterestwascenteredaroundtheidentifyingany

organicmoleculesthatcouldindicatelife.

GasExchange

Designedtolookforgasesgivenoffbyanincubatedsoilsample.

Metabolismbylivingorganismsshouldresultinchanging

concentrationsofseveralgasesincludingoxygen,carbondioxide,

methane,nitrogenandhydrogen

LabeledRelease

DesignedtotestasampleofMartiansoilinoculatedwithadropof

verydiluteaqueousnutrientsolution.Thenutrientsweretaggedwith

radioactive14Candtheairabovethesoilwasthenmonitoredforthe

evolutionofradioactive14CO2gas(possiblyindicatingrespiration).This

experimentwasthenrepeated,butthistimethesoilwasfirstheated

toaveryhightemperaturerenderingitcompletelysterile(actingasa

control).

PyrolyticRelease

Thisinvolvedprovidingasoilsamplewithlight,water,carbondioxide

andcarbonmonoxide.Thecarbonwaslabelledwith14C–theidea

beingthatthiswouldbeincorporatedintothebiomassofa

photosyntheticorganism.Afterremovingthegases,thesoilwasthen

bakedathightemperaturestovaporiseanybiomassinthesoil.If14Cwasdetected,itwould

providesomeevidenceforabiologicallifeform.

Theresultsinitiallycausedagreatdealofexcitementwhenasteady

streamofradioactivegases(includingcarbondioxide)werereleased

inthelabelledreleaseexperiment.However,thiswasnotsustained–

subsequentinjectionsofnutrientsdidnotresultinanyreaction.The

findingsfromtheotherinvestigationsfailedtofindanyevidencefor

organicmoleculesonthesurface,asidefromtracesthatweredueto

contaminationofthespacecraftfromEarth.Theexperimentscarried

outbyVikingthereforeremaininconclusive–itispossiblethat

Martiansoilhasbuiltupathinlayerofanoxidantchemicalwhich

reactsstronglywithnutrientstoproduceCO2.

Fig01(above)

Fig02(above)

Fig03(above)

Fig04(above)

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FromVikingtoExoMars

SinceViking,missionstoMarshavefocusedmainlyongeologicalor

atmosphericanalysis.However,thisisabouttochangewiththe

launchoftheESAExoMarsmission(currentlyscheduledfor2016).

Theaimofthemissionwillbetofurthercharacterisethebiological

environmentofMarsinpreparationforroboticmissionsandthen

humanexploration.Datathatisgatheredduringthemissionshould

provideuswithaclearerpictureofwhetherlifehaseverevolvedon

theplanet.

Themissionwillcarryarover(designedandtestedintheUK)whichis

intendedtoactasa‘fieldbiologist’onthesurfaceofMars.Unusually,

thisroverwillcarryadrillthatisdesignedtotakesamplesfromtwo

metresbelowthesurface–wherescientiststhinkthattheremaybe

waterandhencelife.

Theroverwillthendeliversoilandrocksamplestoaninstrument

(calledthe‘Urey’instrument)whichwillgrindthesamplesandexposethemtoafluorescent

dyethatattachestomoleculescontaininganamine(NH2)group.Thedyeiscalledflourescamine,andisahighlyspecificreagent.

Alaserinsidetheinstrumentwillilluminatethesample,causingamine-containingcompounds

labeledwithflourescaminetoappearinadetectoreveniftheyarepresentonlyinminute

amounts.ThedetectorisestimatedtobeonemilliontimesmoresensitivethanViking.Ifamino

acidsorDNAispresent,thereisthereforeaverygoodchancethattheywillbedetected.

AlllifeonEarthassembleschainsofaminoacidstomakeproteinsduringtheprocessof

translationatribosomesinacell.However,aminoacidscanbemadeeitherbyaliving

organismorbynon-biologicalmeans.ThismeansitispossiblethatMarshasaminoacidsand

otherchemicalprecursorsoflifebuthasneverhadlife.Todistinguishbetweenthatsituation

andevidenceforpastorpresentlifeonMars,theUreyinstrumentteamwillmakeuseofthe

knowledgethatmosttypesofaminoacidscanexistintwodifferentformscalled

stereoisomers.Oneformisreferredtoas"left-handed"andtheotheras"right-handed."Justas

therighthandonahumanmirrorstheleft,thesetwoformsofanaminoacidmirroreachother.

Aminoacidsfromanon-biologicalsourcecomeinaroughly50-50mixofright-handedandleft-

handedforms.LifeonEarth,fromthesimplestmicrobestothelargestplantsandanimals,

makesandusesonlyleft-handedaminoacids,withrareexceptions.Comparableuniformity--

eitherallleftorallright--isexpectedinanyextraterrestriallifeusingbuildingblocksthathave

mirror-imageversionsbecauseamixturewouldcomplicatebiochemistry.

AUreycomponentcalledthemicro-capillaryelectrophoresisunithasthecriticaljobofseparatingdifferenttypesoforganiccompoundsfromoneanotherforidentification,including

separationofmirror-imageaminoacidsfromeachother.ThedeviceforsendingtoMarswillbe

asmallversionincorporatingthisdetectiontechnology,whichisalreadyinuseforbiomedical

proceduressuchaslaw-enforcementDNAtestsandcheckingforhazardousmicrobes.

Sourceofinformation:NASAJetPropulsionLaborator

Fig05(below)

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RISKASSESSMENT Overallrisk(provided

safetyproceduresare

followed)=LOWSubstance Hazard Comment

Food

bBIOHAZARDUncookedsamplesoffoodmaybecontaminatedwithmicrobes.)

Somepeopleareallergictosomefoods,especiallypeanuts.

Benedict’ssolutionUsedtotestfor

reducingsugars.

LOWHAZARD Containsslightly-alkalinecoppersulfatesolution,butatconcentrations

whichpresentonlyaLOWHAZARD.Someriskofspittingifheatingtest

tubes.

EthanolUsedtotestforfats(lipids).

FHIGHLYFLAMMABLE

IfBunsenburnersarebeingusednearbyforotherfoodtests,thereisa

seriousfirerisk.

IodinesolutionUsedtotestforstarch.

LOWHAZARDWeareyeprotection,thoughthesolutioninwaterisdiluteandonly

presentsaLOWHAZARD.

BiurettestUsedtotestforproteins.

IIRRITANTUsesverydilutecoppersulfatesolution(LOWHAZARD)andsodium

hydroxidesolutionwhichisIRRITANT(notCORROSIVE)ifkeptdilute(below

0.5M).

Additionalcomments:

• Donottastefoodsinlaboratories;avoidusingproductscontainingpeanutsetcifthereisaknownallergy.Wear

eyeprotectionandusethesmallestpossibleamountsofchemicals.Heatwithawaterbath.Donotuseethanoliftherearenakedflamesnearby.

• Providedthatconcentrationsofreagentsarekeptasrecommendedaboveandthatawaterbathisusedforheating,therisk

forthesetestsislow.Themainhazardcomesfromethanolwhichishighlyflammable–nakedflamesshouldnotbeallowed

anywherenearethanolforthisreason.

• Eyeprotectionshouldbewornthroughoutallofthepracticalproceduresandlatexglovesarealsodesirabletopreventskin

irritationfromthereagentsused.

Incaseofaccident/incident:

••••••

IntheeyeSwallowedSpiltonskinorclothingClothingcatchesfireOtherethanolfiresSpiltonfloor,bench,etc

Floodtheeyewithgently-runningtapwaterfor10minutes.Seeadoctor.

Donomorethanwashoutthemouthwithwater.Donotinducevomiting.Sipsofwatermayhelpcool

thethroatandhelpkeeptheairwayopen.Seeadoctor.

Removecontaminatedclothing.Drenchtheskinwithplentyofwater.Ifalargeareaisaffectedor

blisteringoccurs,seeadoctor.

Smotherflamesonclothingorskinwithafireblanketorothermaterial.Coolanyburntskinwith

gently-runningtapwaterfor10minutes.Allowfiresinsinks,etctoburnout.

Firesatthetopoftesttubes,beakers,etcshouldbesmoth-eredwithadampclothorheat-proofmatif

thiscanbedonesafely.Forsmallamounts,useadampcloth.Rinsewell.Forlargeramounts,coverwith

mineralabs-orbent(eg,catlitter)andscoopintoabucket.Neutralisealkaliwithcitricacid.Rinsewith

water.

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ImageReferences:

Figure01-ASTROBIOLOGYMagazine(2012)AlienSafari;AlienvsPredator[WWW]Credit:

NASA/JPL/MalinSpaceSciencesSystemAvailablefrom:http://www.astrobio.net/debate/3062/alien-vs-predator[03/12/2012]

Figure02-THEENCYCLOPEDIAOFSCIENCE;ASTROBIOLOGY(dateunknown)VikingLabeledRelease(LR)experiment[WWW]http://www.daviddarling.info/encyclopedia/V/VikingLR.html

[03/12/2012]

Figure03-KIMBALL,J(May2012)Is(Was?)ThereLifeonMars?[WWW]

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/M/Mars.html[03/12/2012]

Figure04-KIMBALL,J(May2012)Is(Was?)ThereLifeonMars?[WWW]

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/M/Mars.html[03/12/2012]

Figure05-DLR;PRESSRELEASES(2009)PressReleases2009[WWW]Credit:ESA-AOES

Medialabhttp://www.dlr.de/en/desktopdefault.aspx/tabid-5105/8598_read-20530/gallery-

1/gallery_read-Image.1.11546/[03/12/2012]

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MartianDeathRays...

Background:

CouldtherebelifeonMars?Perhapsso,althoughthehighintensityofUVlightmeansthatitisunlikelytobefoundonthesurface.Thefollowingexperimentwilldemonstratewhythisisthecase.

BacterialcellscontainDNAjustasplantandanimalcellsdo,andtheDNAincellsisdamagedbyUVradiation.OnEarthwehaveouratmosphere,particularlytheozonetoprotectourDNAfromharmfulUVradiation.Marshoweverhasnoozonelayerandsoitssurfaceisnotprotectedfromthisradiation.FollowthemethodbelowtoseetheeffectofUVlightoncellularlifeforms(bacteria).TheexperimentismainlyaimedatKS5,butcanbeadaptedtolowerkeystagesasrequired.


• Microbiology• Cellbiology• Aseptictechnique• HowScienceWorks–collecting,analysing(viastatisticaltests)andinterpretingdata

Equipmentlist:

• UVcleaningdevice• 4nutrientagarplatespergroup• 4sterileswabspergroup• 1dirtyplace–computerkeyboardsareidealastheyaredifficulttoclean• Tape• Markerpen• Accesstoanincubator

Method:

1. Takeasterileswabofanareaonthekeyboardthatisoftenused.2. Wipetheswabcarefullyacrosstheagarplatebeingcarefulnottodisruptthesurfaceofthe

agar.3. Replacethelid,tapeattwopointsandlabelattheedgewithamarkerpen.4. Repeatsteps1-3foranotherareaonthekeyboard.5. UsingtheUVcleaningdevice,cleanthekeyboardbyholdingitabout2cmawayfromthe

surfacefor10-20secondsineacharea.6. Repeatsteps1-4forthesametwoareasonthekeyboard.7. Incubatetheagarplatesat20⁰Cfor48hours.

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Discussion:

Thepicturesbelowshowthesamplestakenbeforethekeyboardwascleaned.

Thepicturesbelowshowthesamplestakenafterthekeyboardwascleaned.

UVlighthassufficientenergytobreakapartorganicmolecules,includingDNA.BecauseDNAisdamagedbyUVlight,cellsarepreventedfromreproducingandthisreducesthecolonycountforareasthathavereceivedUVtreatment.

Youcancountthenumberofcoloniesoneachplatebydividingitintosectorsusingamarkerpen.Ahandlenscanthenbeusedtoscrutiniseeachsectorforbacterialcoloniesandthemarkerpenusedtostrikethrougheachcolonyasitiscounted.CountthenumberofcoloniesvisiblebeforeandafterUVexposure.

Onceyouhaveobtainedsomenumericaldata,youshouldthenconsiderrepeatingtheinvestigationseveraltimes(poolingclassroomdata)andanalysingtheresultsusinganappropriatestatisticaltest(e.g.95%confidencelimitsand2xstandarderror)–thiswilldeterminewhetherthereisanysignificantdifferenceinthenumberofbacterialcoloniesbeforeandafterUVexposure.

Figures1-4–above

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Backgroundinformation-Mars

LIFEONMARS?THEVIKINGLABELEDRELEASEEXPERIMENT*

GILBERTV.LEVINandPATRICIAANNSTRAAT

BiosphericsIncorporated,Rockville,MD20852,U.S.A.1977

Vikingradiorespirometry("LabeledRelease"[LR])experimentsconductedonsurfacematerialobtainedattwositesonMarshaveproducedresultswhichonEarthwouldclearlyestablishthepresenceofmicrobialactivityinthesoil.However,twofactorsonMarskeepthequestionopen.First,theintenseUVfluxstrikingMarshasgivenrisetoseveraltheoriespostulatingtheproductionofhighlyoxidativecompounds.Suchcompoundsmightberesponsiblefortheobservedresults.Second,themolecularanalysisexperimenthasnotfoundorganicmatterintheMarssurfacematerial,andtherefore,doesnotsupportthepresenceoforganisms.However,sensitivitylimitationsoftheorganicanalysisinstrumentcouldpermitasmanyasonemillionterrestrialtypebacteriatogoundetected.

TerrestrialexperimentswithUVirradiationofMarsAnalogSoildidnotproduceMarstypeLRresults.Gammairradiationofsilicageldidproducepositiveresults,butnotmimickingthoseonMars.Thelifequestionremainsopen.

TheVikingLabeledRelease(LR)Experiment(LevinandStraat,1976)hasobtainedresultsconsistentwiththepresenceofmicrobiallifeonMars.IntheLRexperiment,adiluteaqueoussolutionofsimple,uniformlylabeledcarboncompoundsisappliedtoasampleofsoilinasealedtestcell.Theheadspaceatmosphereinthechamberismonitoredfortheappearanceofradioactivegas.Apositiveresponseistestedforbiologicallabilitybyrepeatingtheexperimentafterheatingaduplicateportionofthesampleto160°Ctosterilizeit.Testsconductedwithterrestrialsoilscontainingviablemicroorganismsinvariablyproducepositiveresponsesand,underfavorableenvironmentalconditions,gasevolutionplottedasafunctionoftimerevealstheclassicmicrobialgrowthcurvewithlag,exponentialandstationaryphasesclearlydefined.

PriortoVikinglaunch,acarefullycontrolledLRexperimentwasconductedinasisterinstrumenttothoseflowntoMars.Theatmosphericcompositionandpressure,thewatervaporcontentandthetemperatureofthetestcellcontainingaCaliforniasoilwitharichmicrobialpopulationwerecontrolledtosimulateconditionsanticipatedwithinthetestcellonMars.Theresultsoftheactiveand

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controlcyclesarepresentedinFig.1asthecumulativeevolutionofradioactivegasoverMartiansols(1sol=24.6h).AtthepointindicatedinFig.1,asecondaliquotoftheradioactivenutrientwasinjectedontothesoilwhichimmediatelyproducedafreshradiorespirometricresponse.Inthecontrolsequence,aduplicateportionofthissoilwasheatedto160°Cfor3handpermittedtocoolpriortonutrientinjection.AsseeninFig.1,essentiallynogasevolved.

*PresentedattheFifthInternationalConferenceontheOriginofLife,Kyoto,Japan,April5-10,1977.

Asofthiswriting,twoactivecyclesoftheLRexperimenthavebeenperformedateachofthetwoMarslandersitessome4000milesapart.Allfouractivecycleshaveyieldedpositive,andsurprisinglysimilar,resultsupontheirfirstinjections.However,ratherthanproducingadditionalgas,subsequentinjectionsineachcyclehaveallproduceddiminutionsintheaccumulatedquantityofradioactivegasalreadyevolved.Typicalresults,thoseforVL-1,Cycle3,arepresentedinFig.2.Duringthislongincubation,atotalofthreenutrientinjectionsweremade.Thefirstproducedastrongpositiveresponse,butthesecondandthirdwerefollowedbyadeclineintheamountofradioactivegasevolvedbythefirst,indicatingadrasticchangeorlossoftheactiveagentinthesoilsometimepriortothesecondinjection.

Figure5–below

5

Fig.3summarizesthecurrentfirstinjectiondataatVikingLander1.TwoactivecyclesandonecontrolcyclearepresentedonascalecomparabletothatusedinFig.1topermitreadycomparisonoftheMarsandEarthresults.Similarly,thecurrentfirstinjectionresultsatVikingLander2aresummarizedinFig.4tothesamescale.

ComparisonoftheresultsfromallfourMarsactivecyclestotheresultsobtainedfromterrestrialsoilundersimulatedMarsconditions,Fig.1,showsthat,withrespecttothefirstinjection,theresponsesaresimilarinmagnitudeoverthetimespanmeasured.TheshapesofthefirstinjectionportionsoftheactivecyclecurvesonMarsandonEarthdifferinthattheMarsresponsesapproachplateauearlierinthetimecourse.Nonetheless,thesimilarityamongallfouractivetestsonMarsisstriking.Thisisdespitethefactthatoneoftheexperiments,VL-1,Cycle3,wasconductedonasampleobtainedbymovingarockwhichhadprotecteditfromUVradiationformanythousandsofyears.Itisinterestingtonotethat,whiletheMarsdatafailtoshowevidenceofexponentialgasevolution,fromwhichgrowthmightbeinferred,neitherdotheterrestrialmicroorganismsundertheimposedMartianconditions.The160°Cpreheatedcontrolsamplesproducedsimilar,lowlevelresultsonEarthandMars.

AlthoughtheLRresultsareconsistentwiththepresenceoflifeonMars,otherfactorspreventtheindicatedconclusionatthistime.ExperimentersfortheothertwoVikinglifedetectionexperiments,PyrolyticReleaseandGasExchange,havestated(Horowitz,1977)thattheirexperimentshaveproducednoconfirming

Figure6–below

Figure7–below

6

evidence.Also,theMolecularAnalysisExperiment(Biemann,1977)hasfoundnoevidenceoforganicmatterintheMartiansurfacematerial.However,thesensitivitythresholdforthisexperimentcouldpermit106terrestrialtypebacteriatogoundetectedprovidedtheywerenotaccompaniedbyorganicdebrismanytimestheirownmassasisgenerally,ifnotalways,thecaseinterrestrialsoils(Biemann,1977).

VarioushypothesesthatexoticMartianconditions,principallythehighUVflux,couldproduceactivestatesorhighlyoxidativecompoundsintheMarssurfacematerialledtospeculations(LevinandStraat,1976)thatphysicalorchemicalprocessesmightfalselyindicatethepresenceoflife.TheearlyreceiptofapositiveactivecycleandanegativecontrolfromtheLRexperimentonMarsintensifiedspeculationonthesehypotheses.

Withintheseverelimitationsofthespacecraftinstrument,theauthorsattemptedvariationsintheLRexperimentsoonafterthepositiveresultsonMarsinanattempttoresolvethedilemma.Thecontrolpretreatmenttemperaturewasdroppedto50°C(actuallyapprox.51.5°C)(LevinandStraat,inpress)onthetheorythatmicroorganismsonMarswouldbeseverelydamagedevenat50°C,atemperaturebeyondtheirexperience,butthatphysicalorchemicalphenomenoncausingthebreakdownofthenutrientwasfarlesslikelytobedegradedbythisrelativelymildtreatment.TheresultsshowninFig.4forVL-2,Cycle2,indicatesevereattenuationoftheLRreaction.However,thestrangekineticsarousedsuspicionthattheLRinstrumenthadmalfunctioned.Aseriesofengineeringtestsremotelyconductedontheinstrumentfailedtodetectanymalfunctionandasubsequentactivecycle,Cycle3,Fig.4,produceda"normal"activeLRcurveforMars.Nonetheless,thesignificanceofthereducedresponsefollowingheatingto50°Crequiredthattheeffectbeconfirmed.Accordingly,Cycle4,inwhichafreshsamplewaspreheatedtoonly46°C(LevinandStraat,inpress),wasconducted.TheresultsconfirmedthemajorreductionintheLRresponseachievedbymildheatingalthough,thistime,thestrangekineticswerenotevident.(Therelativelyminorfluctuationsintheradioactivitycurvescorrelatewithtemperaturechangesimposedonthetestcellbythelander'stemperaturecontrolmechanismasitreactstothediurnaltemperatureswingonMars.)

7

SimultaneouswiththeattemptstoresolvethelifeissueonMars,theauthorsundertookaseriesoflaboratorysimulationexperiments.Theexperimentsreportedhereinwerecomplementarytothe"undertherock"experimentconductedonMarsinthattheysoughttodeterminewhetherexposureofsoiltoradiationmightmimictheLRresults.A"worstcase"testofthetheoriesthationizingradiationofoxygen-richmineralsmightactivatesitescapableofdegradingoneormoreoftheorganicsubstrates(LevinandStraat,1976)comprisingtheLRmediumwaseffectedthroughtheirradiationofpuresilicagelwithgammaraysemittedfromacobalt-60source.SilicagelwasselectedbecauseitwasalmostpureSiO2forwhichconsiderableevidencehasbeencited(Zelleretal.,1970;Zeller,1976)concerningitsactivationbysolarfluxprotonsorharder,ionizingradiation.Moreover,SiO2,intheformofsilicagel,wouldprovideenormoussurfaceareatocontacttheLRmedium.Davisonsilicagel,grade950*wasselectedforuse.Itstypicalchemicalanalysisonapercentdryweightbasisis:99.85%SiO2;ironasFe2O3,0.005%;sodiumasNa2O,0.004%;calciumasCaO,0.018%;titaniumasTiO2,0.058%;andzirconiumasZrO2,0.030%.Surfaceareaisgivenas700m2/g.Maximumtotalvolatilecontentat1750°F(954.4°C)is6.5%.

Sampleswerepreparedinthefollowingmanner.Samples(0.5g)ofthesilicagelwereplacedintoeither7mlglassampoulesor1.5mlquartzampoules.Allampouleswerethenheattreatedat160°Cforthreeormorehoursundercontinuouslymaintainedvacuum.OneatmosphereofC02wasintroduceduponcoolingandtheampoulesweresealed.Theampouleswerethenheatsterilizedat160°Cforaminimumof2.5h.Theglassampouleswerethenpackedindryiceandreceived0.83Mradofcobalt-60gammairradiation.TheyweremaintainedindryiceduringshipmenttotheBiosphericslaboratorywheretheywereimmediatelyplacedinacoldroommaintainedat4°C.Thepurposeofthecoldtreatmentwastominimizehypothesized(DanielliandPlumb)temperatureinducedannealingsofanydisjunctionsordefectsinthesilicagelproducedbytheirradiation.

Figure8–below

8

Thesilicagelinquartzampouleswastreatedinthesamemannerasjustdescribedfortheglassampoules.ThesesampleswerethenSubjectedtoUVirradiation.TheUVsourceconsistedof10Rayonett,2,537Ålamps(15wattsperlamp)arrangedina10inchdiametercircle.Theampouleswereplacedontheirsidesformaximumsurfaceexposureofthesilicagelandwerestationedatthebottomcenterofthecircleoflamps.Theywereirradiatedcontinuouslyfor14daysatapprox.25°C.Thephysicalconstraintsmadeitimpossibletomaintainthesesamplesindryiceduringirradiation.However,immediatelyafterirradiation,theywerepackedindryicewheretheyweremaintainedduringshipmenttoBiosphericsandintroductionintothe4°Ccoldroom.

*DavisonSilicaGelSelectiveAdsorptionGrades,TechnicalBulletin,AdsorbentsDepartment,DavisonChemicalGradeCo.

PriortoconductingLRexperiments,oneseteachofduplicateampoulesexposedtogammaandUVradiationweregiventhefollowingrespectiveheattreatmentsfor3h:4°C,50°C,and160°C.AllheatedsampleswerethenreturnedtothecoldroomwhereLabeledReleaseexperimentswereconducted.Eachampoulewasbrokenandthesilicagelcontentstransferredasepticallytosterilizedglassvialsof25cccapacity.0.1mlofVMlflight-typeLabeledReleasemediumwaspipettedontoeachportionofsilicagel.Absorbentpads(20mmdiameter,No.470,SchleicherandSchuell)placedinsidetheglassvialscrewcap,werequicklymoistenedwithtwodropsofafreshlyprepared,saturatedsolutionofBa(OH)2.Thesecapswereimmediatelyscrewedontocollectevolved14CO2.Incubationwasmaintainedatthe4°Ctemperatureoftheroom.Asacontrolagainstcontaminationandacheckonthenoiselevelofthemedium,duplicateportionsofthesterileVMlalonewereincubated.Atintervalsrangingfrom15mininitiallytoamaximumofonceperdaytowardtheendoftheexperiment,theglassvialcapswereremovedandimmediatelyreplacedwithfreshonescontainingBa(OH)2moistenedpads.Allpadsexposedforthecollectionofradioactive14CO2weretransferredtoplanchets,driedandcountedforradioactivityinagasflowcounter.

Theresults,adjustedforinstrumentsensitivityandscaledtopermitdirectcomparisonoftheMarsandEarthresults,arepresentedinFig.5.Fig.5Apresentsthedataonevolvedradioactivityfromnon-irradiatedsilicagelsubjectedtothevariousheattreatments.AllsamplesofsilicagelevolvedanamountofgaswithinthetypicalsterilecontrolrangefortheLabeledReleaseexperiment.Nosignificantdifferencesareattributedtotheheattreatments.Theresultsofthegammairradiatedsamples,however,Fig.5B,showthatgammairradiationhasapronouncedeffectonthenon-biologicalactivityofthesilicagel.ThesamplesapproachtheactivitylevelsseenforterrestrialorganismsunderMartianconditionsinFig.1andfortheMarsdatapresentedinFigs.3and4.Allfigureshavebeendrawntoapproximatelythesamescaletofacilitatevisualcomparison.The160°Cheatingofthesilicagelsignificantlyattenuateditsresponse.However,themagnitudeoftheeffectdoesnotapproachthatonMarswherethe160°Cpreheattreatmentvirtuallyeradicatedtheresponse.Althoughtheduplicatesforthenon-heatedsamplesandthesamplesheatedto50°Coverlap,theremaybeaslight(approx.10%)reductioninsilicagelreactivityfollowingheatingat50°C.Again,however,theeffectdoesnotapproachthemagnitudeoftheresponse

9

attenuationcausedbyheatingtheMarssampleto50°C.

ResponsesfromtheUVirradiatedsamplesarepresentedinFig.5C.AllareessentiallywithintherangeofcontrolresponsescharacterizingheatsterilizedsoilstestedintheLRexperiment.

Upontheconclusionoftheexperiment,0.5mlofdistilledwater(pH6.3,unbuffered)wasthenaddedtoeachremainingportionofthesampleanditspHdetermined.TheresultsarepresentedinTable1.Theremaininghalfofeachsamplewasplatedontrypticase-soyagartocheckforsterility.Thematerialwasshakenoutoftheglassvialinwhichithadbeenincubatedanddispersedontheagarplatebyagitatingtheplate.Afterincubatingatroomtemperatureforfourdays,allplateswerenegativeforcolonies.

Figure9–below

Figure10–below

10

Anidenticalsetofexperimentswassimultaneouslyperformedonaportionof

theMarsanalogsoil(Clarketal.)preparedbytheVikingInorganicAnalysisTeam

inaccordancewithX-rayfluorescenceanalysesperformedonMars.The

compositionoftheMarsanalogsoilispresentedinTable2.Theresultsofthis

experimentarepresentedinFig.6.Initsnon-irradiatedcondition,theMars

analogsoil,Fig.6,producedgasevolutioninsignificantlygreaterquantitiesthan

didnon-irradiatedsilicagel.Thereisessentiallynodifferencebetweenthenon-

heatedMarsanalogsoilsampleandthesamplepreheatedto50°C.The

magnitudeoftheresponsesapproach50%ofthoseobtainedfromMars.The

apparentdiminutioninresponseofthesamplepreheatedto160°Cmaybean

artifactinthattheveryearlyportionofthecurveshowsthisresponseexceeding

theotherspriortoasharpbreakintheslopewhichmayreflectagasleakor

otherlossofthatday'scollection.Fig.6BshowsthatexposureoftheMarsanalog

soiltogammairradiationdidnotincreaseitsreactivitywithVM1.Norisany

significantattenuationinresponseattributabletotheheattreatmentindicated.

However,allresponsesareabovenormalcontrollevelsfortypicalsterilizedsoils

examinedintheLRexperiment.UVirradiationoftheMarsanalogsoil,asshown

inFig.6C,resultedinadiminutioninallresponsesproducingresultsat,ornear,

thenormalsterilizedsoilcontrollevels.

Figure11–Pleaseseebelow

11

ThepHofeachportionoftheMarsanalogsoilwasdeterminedinthesamemannerasforthesilicagelsamples.TheresultsareshowninTable3.SterilitytestswereperformedonallportionsofMarsanalogsoilattheterminationoftheLRexperimentidenticallyasdescribedforthesilicagel.Allplateswerenegative.

Discussion

ThegammaradiationlevelsinthevicinitiesoftheVikingspacecraftonMarshavenotyetbeenmeasured.However,theymustbelowinthatthebackgroundlevelsmonitoredbytheLRradioactivitydetectorscorrespondextremelycloselytothegammalevelsanticipatedfromtheradioisotopicthermoelectricgenerators(RTGs)carriedoutbytheVikinglanders.Anyexternalgammacontributiontothebackgroundreadingsmust,therefore,beminor.ThebackgroundlevelfortheflightLabeledReleaseinstrumentonEarth,withouttheinfluenceoftheRTGs,isapprox.10cpm.Thus,the0.83MradgammadoseadministeredtothesilicagelandMarsanalogsoilsamplesrepresentsanaccumulateddoseoveralongperiodoftimeonMars.ThiscombinationofaseveregammadoseadministeredtoasubstancehighlysusceptibletosustainingdefectsdidcauseasignificantreleaseofradioactivegasfromtheVMlapproximatingthatoftheLRMarsresponseinmagnitude,butnotinkinetics.PretreatmentoftheirradiatedsilicagelatelevatedtemperaturesresultedindecreasedLabeledReleaseactivityfollowing



12

nutrientinjection.ThisisevocativeoftheLRMarsdata,butthetemperatureeffectonsilicagelisgreatlymutedwithrespecttothatonMars.

TheUVfluxincidenttothesurfaceofMarshasbeenestimated(Glasston,1968)at2X10-4Wcm-2.Currentestimates(Shorthill,pers.comm.)indicatethatonly50%ofthisUVfluxreachestheMartiansurface,yieldingafluxatthesurfaceof10-4wattsor103ergssec-1.BasedonanestimatedUVdoseof10,000µWcm-2,or105ergssec-1,incidenttothesamplesfromtheirradiationarray,theUVirradiationgiventhesamplesexceedsthatonMars,byapproximatelytwoordersofmagnitude.TheLRresponseproducedbyUVirradiatedMarsanalogsoilisevenlessthanthatproducedbynon-irradiatedMarsanalogsoil.Thus,theresultsofthesetwotestsoftheMarsanalogsoilmakeitunlikely,iftheMarsanalogsoilisafaithfulrepresentation,thatultravioletirradiationisresponsiblefortheresultsobtainedonMarsintheLRinstrument.Whilethepositiveresponseofthenon-irradiatedMarsanalogsoilanditspossiblepretreatmenttemperaturedependencyareofinterest,thefactthatitscapabilitytoproducegasfromVMlisUV-labilemakesitanunlikelyexplanationoftheMarsresults.Theanalogsoiltestedcontainedalpha-Fe2O3.Recently,ithasbeensuggested(Oyama,VikingBiologyTeam)thatepsilon-Fe2O3mightbetheformonMarsandthatitmightreactwithorganiccompounds.Accordingly,theVikingInorganicAnalysisTeamispresentlypreparinganotherMarsanalogsoil,similartothefirst,butcontainingepsilon-Fe2O3.TheauthorsplantotestthismaterialforpossibleactivityintheLRexperiment.

Conclusions

1. TheVikingLabeledReleaseExperimenthasproducedevidenceforlifeonMars.However,non-terrestrialsoilchemistrymaybemimickingabiologicalresponse.Allhypothesesrequirefurtherstudybeforeaconclusioncanbereached.

2. IntensegammairradiationofsilicagelcausesevolutionofgaswhentheLRVMlmediumisappliedtoit.TheamountofgasevolvedapproachesthatobservedintheLRexperimentonMars.However,whilesomepretreatmenttemperaturedependencywasobservedinthesilicagel,theeffectsarenotasgreatasthoseobservedintheMarsexperiments.This"worstcase"testisextremeinthatthegammalevelsonMarsdonotapproachthedosageappliedinthetest.However,thereactionisofsufficientinterestthatitwillbeexploredfurtheranditspossiblerelevancy,totheLRMarsresultsstudied,perhapsasananalogoflong-termexposuretothesolarwind.

3. NosignificanteffectwasobservedintheLRexperimentwhensilicagelwasirradiatedbyUVlight.

4. Non-irradiatedMarsanalogsoilproducesaresponseintheLRexperiment.Theresponsemayshowsomeslightpretreatmenttemperaturedependency,butnotofthemagnitudeobservedonMars.

5. GammairradiationoftheMarsanalogsoilhadnoapparenteffectintheLRexperiment.

6. UVirradiationoftheMarsanalogsoilreducedtheLRresponsetowellwithinthosenormallyobservedfromsterilizedsoils.ItisthusunlikelythattheMars

13

resultscanbeattributedtoafactorintheMarsanalogsoil.

Conclusions3and6inconjunctionwiththeLRMarsdataobtainedfromthe"undertherock"sampletendtoeliminateUVradiationascausativeoftheLabeledReleaseresponse.

UpdatedversionsoftheMarsanalogsoil(includingepsilon-Fe2O3)willbetestedwithandwithoutgammairradiationintheLabeledReleaseTestStandardsModule(TSM)(LevinandStraat,1976)wheretheycanbemaintainedundersimulatedMarsconditionsthroughouttheincubationperiod.TheeffectofadditionalinjectionsofnutrientcanbestudiedintheTSMforcomparisonwiththeMarsresults.

14

RISKASSESSMENT Overallrisk(providedsafetyproceduresarefollowed)=LOW

Substance Hazard CommentBacterialcolonies

BIOHAZARD

Agarplateswillcontainnumerousbacterialcoloniesathighconcentrations.Theymustremainclosedatalltimes,andsealedviatwostripsofsellotapeeithersideofthedish–incubateatatemperaturenohigherthan20°C.Cottonswabsusedtosampledifferentareasshouldbedisposedofinthedisinfectantsolutionprovided.Agarplatesshouldbedisposedofinanautoclaveafteruse.

UVlight HAZARD UVlightisdamagingtoskincellsandalsocellsoftheretina.ExposuretoUVlightfromthesterilisingprobeshouldbepreventedatalltimes

Cottonswab

LOWHAZRAD

Possiblyharbourspathogenicmicrobesafterbeingusedforsampling.However,theconcentrationsofmicrobeswilllikelybeatalowlevelpriortoincubationonagar.Cottonswabshouldbedisposedofusingthesterilesolutionprovided.

Additionalcomments:

• Washhandsthoroughlybeforeandafterprocedureandwearlatexglovesifavailable

• Agarplatesshouldbesealedwithonlytwostripsofsellotapeateithersideoftheplate,topreventanaerobicconditionsdevelopingandpathogenicbacteriabeinggrown.

• Undernocircumstancesshouldtheagarplatesbeopenedonceincubationhasbegun.

• Agarplatesmustbedisposedofusinganautoclaveattheendoftheinvestigation

• EnsurethattheUVprobeisswitchedoffwhennotinusetopreventaccidentalexposuretoUVlight


••

ExposuretoUVlightExposuretobacterialcolonies

Dependingonthelengthoftimethattheexposurewasfor,seekmedicaladvice.Ifskincontact,immediatelywashaffectedareawithsoapandwarmwater.Antisepticsolutionsorwipesmayalsobeusedtocleanaffectedarea.Re-sealanyagarplatethathasbecomeexposedandarrangefordisposalviaautoclave.Seekmedicaladvice.

15

ImageReferences:

Figures1-4-OwnedbyChristopherCarr–AuthorofClassroomActivity#2

Figure5-GILBERTV.LEVINandPATRICIAANNSTRAAT(1977)LIFEONMARS?THEVIKINGLABELEDRELEASEEXPERIMENT*[WWW]Copyright:Elsevier/North-HollandScientificPublishers,Ltd.http://mars.spherix.com/lifemars/lifemars.htm[03/12/2012]









1


What’syourlimit?

Background:

PhysicalconditionsonotherplanetsandmoonsareunlikelytobewithinthesamerangesasthatexperiencedbyEarth.However,asignificantdegreeofvariancefrom‘ideal’rangesmaybetolerableforasmallnumberoforganismsknownasextremophiles.Theseareorganismswhichcanwithstand(andeventhrive)inextremeenvironmentsonEarth,includingthoseoftemperature,pHandsalinity.Thisinvestigationlooksattheeffectsofsubjectingalivingorganism(yeast)tosomeextremeconditionsandobservingchangestoratesofreaction–indicatingtherangesatwhichitcansurvive.TheinvestigationisaimedmainlyattheupperendofKS3orKS4.However,itispossibletoadapttheinvestigationintoaformmoresuitableforKS5ifrequired.


• Respiration• Cellbiology• Enzymes&ratesofreaction• HowScienceWorks–collecting,analysing(viastatisticaltests)andinterpretingdata

Equipmentlist:

• Emptywaterbottles(250ml)• Balloons• Driedyeastgranules• Glucose• Whitevinegar• Wateratdifferenttemperatures–hot,warmandcold• Markerpen• AndrewsSalts(dissolveinwatertocreateanalkalinesolution)• Salt(tocreatesolutionsofdifferentsalinities)

Method:

Theinvestigationinvolvessubjectingsomepre-preparedyeastsamplestodifferentconditionsoftemperature,pHandsalinity.Amixtureofyeastandglucoseishydratedwithwaterinsideabottle,withaballoonplacedonthetoptogaugetheamountofcarbondioxideproduced,andhenceactivityoftheyeast.Thetasksheetsthatfollowgivefulldetailsofthemaininvestigationsbutitisimportanttonotethefollowingdetailsregardingtheinitialsetupofapparatus:

• Youwillneedtofirstsetupseveralbottleseachcontainingtwoteaspoonsofglucoseandfourteaspoonsofyeast.Eachgroupintheclasswillneedthreebottles.

• Thebottlescanbepre-markedwithlinesthatshowapproximatevolumesofwaterorothersolutionsrequired.

• Theyeast,glucoseandwatermustbefirmlyshakenforabout30secondsbeforetheinvestigationcommences.

2

• Theresultsoftheinvestigationarenotinstantaneous–youwillneedtoplanforatleast30minuteswhileballoonsbecomeinflatedbycarbondioxideproducedfromtheyeast.Thiswouldbeagoodtimeforstudentstoanswerquestionsonthetasksheetsandfeedbacktheirpredictionstothewholeclass.

• Theinvestigationhasplentyofscopefordevelopments,refinementsandimprovements–studentsshouldbeencouragedtocarryoutanevaluationaftertheinvestigationisover.

Discussion:

Afterabout30minuteshaselapsed,askeachgrouptocometothefrontoftheclassandholdtheirbottlesup(withpartiallyinflatedballoons).Askeachgrouptodescribethedifferencesbetweentherelativeamountsofballooninflationandthenexplainusingtheirknowledgeofenzymes,cells,ratesofreactionand/orosmosis:

Temperature–warmtemperaturewillshowgreatestrateofinflation,duetoenzymesinyeastbeingclosesttotheiroptimumtemperature.Coldtemperatureswillshowlittleinflationduetoreducedkineticenergyandhenceratesofreaction.Hottemperatureswillshowlittleinflationduetodenaturationofsomeenzymes.

pH–theenzymesinyeastgenerallyhaveoptimumvaluesclosetopH7.Therewillbelittleinflationinacidicoralkalineconditionsduetothedenaturationoftheseenzymes.

Salinity–theadditionofsaltlowersthewaterpotentialofthesolutioninthebottle.Themoresaltadded,thelowerthewaterpotentialbecomesresultinginwaterlossfromyeastcells(andtheirsubsequentdeath).Inflationoftheballoonswilllikelydiminishasmoreandmoresaltisadded.

3

Meettherecordbreakers...

Finishthelessonwithadiscussionontheextremeconditionsthatlifehasbeenknowntowithstand:

Notethatalltheseorganismsarebacterial–morecomplexlifeformsaresimplytoocomplicatedtowithstandtheseenvironments(themorecomplexsomethingis,themorethereistogowrong!).Findinglifeexistinginextremeenvironmentsmaybepossible,butitisunlikelytoanythingotherthansimplemicro-organisms.

4

FurtherexamplesofEarthlyextremophiles

Cold–TheMcMurdoDryValleysinAntarcticaaresomeofthecoldest,driestdesertsonEarth,withaverageannualtemperaturesof-20oC(-4oF)andlessthan10centimetres(4inches)ofprecipitationayear.Scientistshavefoundbacteriainliquidwaterpocketsembeddedabouttwelvefeetdeepin“solid”lakeice.Someofthesebacteriausechemicalnutrientsfromparticlesofdirtintheiceanduseenergyfromsunlightforphotosynthesis.

Hot–LargeconcentrationsofmicrobesthriveinYellowstoneNationalPark’sGrandPrismaticSprings,ahotspringwithwatertemperaturesupto90oC(188oF).OtherhotspringsinYellowstoneareextremelyacidic,yetarehometomanydifferentkindsofbacteriaandmicrobes.Manyofthesemicrobesusechemicalnutrientsinthewatersandenergyfromsunlightforphotosynthesis.

Deepunderground–Scientistshavediscoveredbacterialivingingroundwater5kilometresbelowthesurfaceindeepgoldminesoftheWitwatersrandBasininSouthAfrica.Thesemicrobesthriveincavitiesandcracksinrocks.ScientistsarealsoareinvestigatinglifewithinandbelowpermafrostinnorthernCanada.

Bottomofthesea–Scientistshavefoundabundantlifeclusteredaroundhydrothermalventsontheoceanfloor,includingbacteria,mussels,clams,shrimp,andgianttubewormsthatcanreachtenfeetinlength.Waterpouringoutoftheventsinthecompletedarknessthousandsoffeetunderthesurfaceoftheseacanreachtemperaturesof113-120oC(235-248oF).Thehighpressureskeepthewaterfromboiling.Bacteriausechemicalsinthevent’swater,primarilyhydrogensulfide,astheirenergysourceinsteadofsunlight.Othercreaturessurvivebyeatingthebacteriaoreachother.

HighAcidity–ThewaterintheRioTintoinsouthwesternSpainisveryacidic,aresultofchemicalreactionsbetweenthewater,andironandsulfurmineralsintheground.Theriverhasadeepredcolor,likewine,becauseofirondissolvedinthewater.Microbeslivinginthewaterusechemicalreactionswithironandsulfurmineralstogeneratetheenergytheyneed.ProductsfromthesemetabolicreactionscontributetothelowpHintheenvironment.Manyalgaeandfungialsoliveintheacidicwaters.

Source:NASA

5

TasksheetYouareinvestigatingtheeffectofpHontherateof

respirationinyeast.Youwillneedtoworktogetherasateamtoensure

thateachexperimenttakesplaceatthesametime,sothatyourresultscanbecompared

Collectthreeofthebottlesthathavebeenpre-

preparedwithyeastandsugarandcollectthreeballoons

Youwillnowneedtovaryakeyvariabledepending

onyourgroup:VaryingpHCollectsomewarmwaterfromawaterbathandaddthistoyourbottlesuntilitreachesthefirstblacklineon

thesideofthebottle.Shakethebottlewelltomixthecontents.• Addasmallvolumeofvinegartoyourfirstbottleuntilthewaterlevelreachesthesecondblackline.Shake

againandwhenyouarereadytostart,immediatelyattachtheballoontotheendofthebottle.• Addasmallvolumeofsodiumbicarbonatesolutiontoyoursecondbottleuntilthewaterlevelreachesthe

secondblackline.Shakeagainandwhenyouarereadytostart,immediatelyattachtheballoontotheendofthebottle.

• Addasmallvolumeofwarmwaterfromawaterbathtoyourthirdbottleuntilthewaterlevelreachesthe

secondblackline.Shakeagainandwhenyouarereadytostart,immediatelyattachtheballoontotheendofthebottle.

Onceyouhavesetthebottlesup,youwillneedtoleavethemtostandforatleast20minutes.Youshouldthen

beabletomakesomecomparisonsbetweenthedifferentbottlesThinkaboutit...............1. Whichbottlesshowedthegreatestrateofrespirationandwhichshowedtheleast?2. WhatsortofpHconditionsdoyouthinkyeastisadaptedtolivein?3. DoyouhaveenoughdatatoestablishtherangeofpHvaluestowhichyeastis

tolerant?Howcouldyouimprovetheinvestigationtogiveamoreaccurateestimateoftherangeoftolerances?

4. ExplainwhychangesinpHwouldaffecttherateofrespirationinyeast5. Whatwasthepurposeofaddingmorewatertoyourthirdbottle?

Figure1–above

Fig.2–above

6

TasksheetYouareinvestigatingtheeffectoftemperatureontherateof

respirationinyeast.Youwillneedtoworktogetherasateamtoensurethateach

experimenttakesplaceatthesametime,sothatyourresultscanbecompared

Collectthreeofthebottlesthathavebeenpre-preparedwithyeast

andsugarandcollectthreeballoonsYouwillnowneedtovaryakeyvariabledependingonyourgroup:VaryingtemperatureYouareprovidedwithcold,warmandhotwaterinthreedifferent

waterbaths.Youshouldnotethetemperaturesofthewaterusingthethermometersprovided.

• Addasmallvolumeofcoldwaterfromthecoldwaterbathtoyourfirstbottleuntilthewaterlevelreaches

thesecondblacklineonthebottle.Shakethebottlewellandwhenyouarereadytostart,immediatelyattachtheballoontotheendofthebottle.

• Addasmallvolumeofwarmwatertoyoursecondbottleuntilthewaterlevelreachesthesecondblackline.

Shakeagainandwhenyouarereadytostart,immediatelyattachtheballoontotheendofthebottle.• Addasmallvolumeofhotwater(CARE!)fromawaterbathtoyourthirdbottleuntilthewaterlevelreaches

thesecondblackline.Shakeagainandwhenyouarereadytostart,immediatelyattachtheballoontotheendofthebottle.

Onceyouhavesetthebottlesup,youwillneedtoleavethemtostandforatleast20minutes.Youshouldthen

beabletomakesomecomparisonsbetweenthedifferentbottlesThinkaboutit...............1. Whichbottlesshowedthegreatestrateofrespirationandwhichshowedtheleast?2. Whatsortoftemperatureconditionsdoyouthinkyeastisadaptedtolivein?3. Doyouhaveenoughdatatoestablishtherangeoftemperaturevaluesto

whichyeastistolerant?Howcouldyouimprovetheinvestigationtogiveamoreaccurateestimateoftherangeoftolerances?

4. Explainwhychangesintemperaturewouldaffecttherateofrespirationin

yeast5. Doyouthinkthatthesurfacetemperatureofaplanetwouldhaveany

implicationsaboutthelikelihoodoffindinglifethere?Explainyouranswer

Figure3–above

Fig.2–above

7

TasksheetYouareinvestigatingtheeffectofsalinityontherateof

respirationinyeast.Youwillneedtoworktogetherasateamtoensurethateach

experimenttakesplaceatthesametime,sothatyourresultscanbecompared

Collectthreeofthebottlesthathavebeenpre-preparedwith

yeastandsugarandcollectthreeballoonsYouwillnowneedtovaryakeyvariabledependingonyour

group:VaryingsalinityCollectsomewarmwaterfromawaterbathandaddthistoyourbottlesuntilitreachesthesecondblacklineon

thesideofthebottle.Shakethebottlewelltomixthecontents.• Addtwoteaspoonsofsalttoyourfirstbottle.Shakewellsothatthesaltdissolvesandwhenyouareready

tostart,immediatelyattachtheballoontotheendofthebottle.• Addsixteaspoonsofsalttoyoursecondbottle.Shakewellsothatthesaltdissolvesandwhenyouare

readytostart,immediatelyattachtheballoontotheendofthebottle.• Donotaddanysalttoyourthirdbottle.Shakewellandwhenyouarereadytostart,immediatelyattach

theballoontotheendofthebottle.Onceyouhavesetthebottlesup,youwillneedtoleavethemtostandforatleast20minutes.Youshouldthen

beabletomakesomecomparisonsbetweenthedifferentbottlesThinkaboutit...............1. Whichbottlesshowedthegreatestrateofrespirationandwhichshowedthe

least?2. Whatsortofsalinityconditionsdoyouthinkyeastisadaptedtolivein?3. Doyouhaveenoughdatatoestablishtherangeofsalinityvaluestowhichyeast

istolerant?Howcouldyouimprovetheinvestigationtogiveamoreaccurateestimateoftherangeoftolerances?

4. Explainwhychangesinsalinitywouldaffecttherateofrespirationinyeast

Fig.2–above

Figure4–above

8

RISKASSESSMENT Overallrisk(provided

safetyproceduresare

followed)=LOW

Substance Hazard CommentYeast

BIOHAZARD

Yeastisamicro-organismthatshouldnotbeingestedorallowedto

entercutsorabrasionsonskinsurfaces.Thoroughwashingofhands

beforeandafteruseisgenerallytheonlyprecautionrequired.

Vinegar LOWHAZARD Weakacid,requiringeyeprotectiontobeworn.Maindangercomes

fromsquirtingoutofthebottleaspressurebuildsduetocarbon

dioxideproduction

Sodiumbicarbonatesolution

LOWHAZARD

Weakalkali,requiringeyeprotectiontobeworn.Maindangercomes

fromsquirtingoutofthebottleaspressurebuildsduetocarbon

dioxideproduction

Hotwater>70°C HAZARD Dangerofscalding.Eyeprotectionmustbewornwhilehandling.

Teachertoarrangeforhotwatertobepouredintoseparatebeakers

whichstudentscanthenuse

Additionalcomments:

• Careshouldbetakenwhenbottlesareshakentohydrateyeast–makesurebottlecapsarefullyscrewedonto

preventanypossibleejectionofthecontents

• Eyeprotectionmustbewornthroughoutthepractical,particularlywhenremoving,inspectingoraddingballoonsaspressure

canbereleasedsuddenlycausingthecontentsofthebottletobeejected


••••

IntheeyeSwallowedScaldsSpiltonskinorclothing

Floodtheeyewithgently-runningtapwaterfor10minutes.Seeadoctor.

Donomorethanwashoutthemouthwithwater.Donotinducevomiting.Sipsofwatermayhelpcool

thethroatandhelpkeeptheairwayopen.Seeadoctor.

Runaffectedareaundercoldwaterforatleasttenminutesandpossiblylongerdependingonextenton

theinjury.Applyasteriledressingandseeadoctorifblisteringoccurs.

Removecontaminatedclothing.Drenchtheskinwithplentyofwater.Ifalargeareaisaffectedor

blisteringoccurs,seeadoctor.

9

ImageReferences:

Figure01-LUXInnovateLtd(2009)Assessmentoferosionsusceptibility[WWW]LUXDSAvailable

from:http://luxds.com/web/index.php?option=com_content&task=view&id=31[04/12/2012]

Figure01-ELMHURST(dateunknown)pHScale–IntroductionandDefinitions[WWW]Availablefrom:http://www.elmhurst.edu/~chm/vchembook/184ph.html[04/12/2012]

Figure02-TOON,MARK(2012)Stickmanhandsonhipslookpuzzledclipart[WWW]MarkToonAvailablefrom:http://www.marktoon.co.uk/cartoons/stickmen/stickman-hands-on-hips-looks-puzzled-clipart.gif[04/12/2012]

Figure03-REIGNOVERUS(09-07-2010)Thesightsofsummer[WWW]Availablefrom:

http://reignover.us/2010/07/[04/12/2012]

Figure04-Land_Fish(04-10-2004)Re:Refractometer@swingarmSGtesters[WWW]Postby–

Land_FishAvailablefrom:http://www.3reef.com/forums/water-chemistry/refractometer-swingarm-sg-testers-32759.html[04/12/2012]

WeAreAliens!–Classroomactivity4(Biology)Cells1. Firstlabelthetwocellsbelowasplantoranimal2. Nowaddtheselabels

nucleuscytoplasmchloroplastcellwallcellmembranevacuole

3.Fillinthetablebelowbylistingthepartsfoundin plantandanimalcells.

Plantcell Animalcell

4.Usecolourstomatchthepartwithitsjob

Part Job

Nucleus Helpstoprovidesupportandcontainscellsap

Cytoplasm Absorbslightenergyforphotosynthesis

Membrane Carriesgeneticinformation

Cellwall Providessupport

Vacuole Manychemicalreactionsoccurhere

Chloroplast Controlsthemovementofsubstancesinandoutofthecell

5.Herearetwostudentmodelsofcells

a) Aretheyplantoranimalcells?b) Addasmanylabelsasyoucan

1

WeAreAliens!–Classroomactivity5(Biology)MakingModelCells

Thecellisthesmallestunitoflifeandalthoughwedon’tknowexactlywhentheyfirstappearedonEarthweknowthatlifearrivedaremarkablyshorttimeafterthebirthoftheplanet.FormanymillenniasinglecelledorganismsweretheonlyformoflifeonEarthandit’sthistypeoflifethatastrobiologistsarelookingforelsewhereinthesolarsystem.Inthisfunactivity,wallpaperpasteisusedtobuildmodelcells.It’sverygoodforhelpingstudentstoappreciatewhatcellsarelikeandisverymemorable.

Equipment• Wallpaperpaste(ensureit’sthealmostcolourlesssortratherthanthetypebasedon

starch)• Smallsealableplasticbags(sandwichbagsareOKbutratherbig.Smallerbagsare

readilyavailableonline.Forexampleyoucanget10003”bagsherefor£6amazonlink)

• Waterproofpen(s)

Tomakemicrobes• Cotton• String• lengthsofwool

Tomakeplantcells• Greentiddlywinks/counters

(chloroplasts)• {Redtiddlywinks/counters

(mitochondria)}• Clingfilm(vacuole)• Marbles(nucleus)

PracticaltipsThewallpaperpasteneedsmakingupbeforethelessonandshouldonlybedispensedbytheteacherunlessyouwantalotofmess.Followtheinstructionsonthepacketbutmakeitupusingthesmallestamountofwaterspecified(ieasifhangingheavypaper).Ifyouwanttoidentifythecellslater,ensurestudentwritetheirnamesonthebagsbeforetheyarefilled.Usethewaterproofpensforthis.Tomakeamodelmicrobe:

1. AddsomelengthsofcottontotheplasticbagtorepresenttheDNAstrands.Youcouldalsoaddsomecottonloopstorepresentplasmids.

2. Theteacheraddsagooddollopofwallpaperpaste

3. Squeezeouttheairandsealthebag.Whentheoutsideofthebagisdry,youmaywanttoensureitstayssealedbyaddingsellotape

4. Usingsellotape,fixalengthofwooltotheoutsideofthebagtorepresentflagella

5. Addseveralshortlengthofthisstringtorepresentpillli

6. Youcanevenusealayerofwallpaperpasteontheoutsideofthebagtorepresentabacterialcapsule.

Figure1–above

2

Tomakeamodelplantcell:

1. Carefullyrunsomewaterintoa“saggy”pieceofclingfilmandthentwistthecornerstogethertomakea“bubble”ofwater.Youmaywanttoaddsellotapetohelpsealit.

2. Placetheclingfilmbubble,marbleandseveralgreentiddlywinks,intoaplasticbag.Ifappropriatetoyourspecificationyoucanalsoaddredtiddlywinks

3. Teacheraddsagooddollopofwallpaperpaste,thensealthebagtofinishthemodelcell

FollowupworkMatchthepartofthemodeltowhatitrepresentsinarealmicrobe

Plasticbag cytoplasmCottonthread cellmembraneWallpaperpaste flagellumWool pilliString chromosome

Matchthepartofthemodeltowhatitrepresentsinarealplantcell

Marble vacuoleGreentiddlywinks cytoplasmWallpaperpaste membranePlasticbagcell chloroplastsClingfilm nucleus

Theonepartofthecellthatwasmissingwasthe__________(cellwall)Thereisalsoasimplereinforcementworksheetoncellsforstudentstocomplete

Figure2–above

3

Takingitfurther(takenfromtheUniversityofUtah’slearngeneticswebsite)SomeoftheoldestcellsonEartharesingle-cellorganismscalledbacteria.FossilrecordsindicatethatmoundsofbacteriaoncecoveredyoungEarth.Somebeganmakingtheirownfoodusingcarbondioxideintheatmosphereandenergytheyharvestedfromthesun.Thisprocess(calledphotosynthesis)producedenoughoxygentochangeEarth'satmosphere.Soonafterward,newoxygen-breathinglifeformscameontothescene.Withapopulationofincreasinglydiversebacteriallife,thestagewassetforsomeamazingthingstohappenThereiscompellingevidencethatmitochondriaandchloroplastswereonceprimitivebacterialcells.Thisevidenceisdescribedintheendosymbiotictheory.Howdidthistheorygetitsname?Symbiosisoccurswhentwodifferentspeciesbenefitfromlivingandworkingtogether.Whenoneorganismactuallylivesinsidetheotherit'scalledendosymbiosis.Theendosymbiotictheorydescribeshowalargehostcellandingestedbacteriacouldeasilybecomedependentononeanotherforsurvival,resultinginapermanentrelationship.Overmillionsofyearsofevolution,mitochondriaandchloroplastshavebecomemorespecializedandtodaytheycannotliveoutsidethecell.ImageReferences:Figure01-RUIZ,MARIANA(dateunknown)GramStainandBacterialCellWallStructure[WWW]Availablefrom:http://tamiport.hubpages.com/hub/Gram-Stain-and-Bacterial-Cell-Wall-Structure#slide2149066[06/12/2012]Figure02-9AREVISION(dateunknown)Thesearethethingsthatplantsneedforphotosynthesis[WWW]Availablefrom:http://9arevision.wikispaces.com/plants[04/12/2012]Figure03-UTAHLEARNGENETICS(dateunknown)EndosymbioticOriginofChloroplastsandMitochondria[WWW]UtahLearnGenetics–EducationAvailablefrom:http://www.uic.edu/classes/bios/bios100/lectures/cells.htm[04/12/2012]

Figure3–above

1

WeAreAliens!–Classroomactivity1(Chemistry)LivingintheFreezer

Thecellsofplants,animalsandbacterialivinginlowtemperatureenvironmentsonEarthoftencontainantifreeze

proteinstopreventtheirbodyfluidsfromfreezing.

Ifthere’slifeanywhereelseinoursolarsystem,it’slikelythatittoowillhavetocopewithcoldconditionsand

needsomesortofantifreeze.

Youcandemonstratetheeffectthatfreezingwaterhasoncellsbydisplayingstrawberries(andotherfruitand

veg)aftertheyhavebeeninthefreezer.Theicecrystalsthatformhavealargervolumethanliquidwaterthey’re

madefromandtheresultingexpansionbreaksopencellwallsresultingin“soggy”strawberries

Inthisactivity,studentsplanandcarryoutanexperimenttofindouttheeffectofanantifreezeonthemelting

pointofwater.Theaimoftheexperimentisconceptuallysimple,allowingstudentstodeveloptheirplanningand

practicalskills.

Theymayalreadyknowthat“grit”containingrocksalt(impuresodiumchloride)isspreadonroadsinthewinter

tostopiceforming.Liquidantifreezesarealsoaddedtothewaterinthecoolantsystemandscreenwashbottles

ofcarstopreventwaterfromfreezingoverthewinter.

Therearetwodifferentmethodsthatcouldbeused.Dependingonthetimeyouhaveavailable,youmightliketo

steerstudentstowardsoneortheother.

1. Findingtheconcentrationneededtostopwaterfromfreezinginadomesticfreezer.Different

concentrationsofantifreezeandusedtofillanicecubetrayandthenplacedinafreezer.Thenext

lesson,studentscanviewtheicecubesandseewhichconcentrationsremainliquid.

2. Findingouthowlongicecubesmadewithdifferentconcentrationsofantifreezetaketomelt.Thelonger

theytaketomelt,thelesseffectivetheantifreeze.Studentsshoulddevisetheirownmethodfor

determiningthemelttimebutsuitablemethodsinclude,placingthecubeinabeakerofwaterandtiming

howlongittakestodisappearandplacingtheicecubeinafunnelheldover10cm3measuringcylinder

andmeasuringthevolumeofwaterproducedinacertaintime.Tosavetime,heicecubescouldbemade

upreadybytechnicians

Usingeitherofthemethodsabove,analternativeinvestigationistodeterminewhichantifreezeismosteffective.

Antifreezestotryinclude:

• Rocksalt

• Puresodiumchloride

• Calciumchlorideirritant

• Potassiumchloride

• Ethan-1,2-diol(ethyleneglycol)(thisistheactiveingredientincommercial

antifreezes)harmful

• Commercialantifreeze

• IMS/IDA/ethanolhighlyflammableandharmful

• Windscreenwasherfluid(oftencontainsethanol)

2

RiskAssessment-refertoCLEAPShazchemcardsandcarryoutyourownriskassessment.

EquipmentListwillvarydependingupontheexactmethodstudentschoosebutitlikelytoinclude

• Oneormoreantifreezes(seeabove)

• Icecubetrays

• Accesstoafreezer

• Foodcolourings

• Measuringcylinders

• Distilledwater

• Balance

• Funnels

• Beakers

• (thermometers–formeasuringwatertemperatureifmeltingicecubes)

PracticalHints

Whenmakingupsolutionsofliquidantifreezes,studentscoulduse10cm3measuringcylinders.

10cm3water =0%antifreeze

9.5cm3water+0.5cm

3antifreeze =5%antifreeze

9cm3water+1cm


8cm3water+2cm


Andsoon

Whenmakingupsolutionsofsolidantifreezesthen%concentrationsareworkedoutmosteasilyw/v(weightfor

volume)

100cm3water =0%antifreeze

100cm3water +5gsalt =5%antifreeze

100cm3water +10gsalt =10%antifreeze

Andsoon

Commercialantifreezesolutionsareoftencolouredandconcentrationscanbeseenbyjudgingthedepthof

colour.Ifstudentsmakeuptheirownicecubes,itisrecommendedthattheyusearowofthetrayforsuccessive

concentrations.Indeliblepenscanbeusedtomarkthetrayswithnamesetc.

Ifmakingupicecubeswithdifferentsaltconcentrations,itcansavealotofconfusioniffoodcolouringisalso

addedtothewater.So,forexample,5%cubesareyellow,10%cubesaregreenetc.

Domesticfreezersusuallyoperateatabout-20oCbutyoumaybeabletogetthemcolderiftheyhavean

adjustablethermostat.Ifyouhavetheoptionof“fastfreeze”youmaybeabletogetdowntoabout-26oC

Followupwork

Adataanalysisworksheetisincludedthatrequiresstudentstodrawabargraphthatincludesnegativenumbers

andinterpretthedataitshows.

Extension

Youcouldgoontoinvestigatetheeffectofanantifreezeontheboilingpointofwater.Studentsmaybesurprised

tofindthatsaltraisestheboilingpointofwater.

1

WeAreAliens!–Classroomactivity1(Chemistry)Antifreezes Name

______________________________(graphpaperrequired)

Anti-freezeliquid

A B C D

FreezingPoint(°C) 10 -6 0 -15

Drawabargraph(ongraphpaper)toshowthisdata.

Beforeyoustart,thinkaboutwherethehorizontalaxisshouldbe.

Useyourgraphorthetabletocompletethiswork.

1. Liquid______hasthelowestfreezingpoint.

2. Liquid______hasthehighestfreezingpoint.

3. Liquid______couldbewater.

4. Liquid______wouldbeuselessasanantifreeze.

5. Liquid______wouldmakethebestantifreeze.

6. LiquidCwillmeltat______°C

7. IfliquidsBandCweremixed,thefreezingpointwouldbeabout_____°C

8. IfliquidsAandDweremixed,thefreezingpointwouldbeabout_____°C

9. Onewinterdaythetemperatureis-2°C.

Liquids______and______wouldactuallybesolidsonthisday.

10. TheaveragetemperatureonMarsis-55°C.

ExplainwhynoneoftheseliquidswouldbeanygoodasanantifreezeonMars

11. EnceladusisamoonofSaturn.Thispictureshowsaplume

oficeandwatergushingintospace.Scientistshave

discoveredthatthewatercontainssalt.Explainwhythis

mighthelpkeepthewateraliquid.

__________________________________________

__________________________________________

__________________________________________

_____________________________________________________________________

_____________________________________________________________________

_____________________________________________________________________

1

WeAreAliens!–Classroomactivity6(Chemistry)UsingUVbeadstoinvestigatereactionrates

OverviewTherateofachemicalreactionishighlydependentontemperature;oftena10oriseintemperaturewilldoubleareactionrate.Thechemicalreactionsthattakeplaceinlivingcellsarenowexception,indeedmanyorganismregulatetheirtemperatureveryaccuratelyforthisreason.Inthisexperimentstudentswillexplorehowratedependsontemperatureinaverydirectmannerwithoutthecomplicationofmeasuringchemicalreactantsoftheirproducts.PhotochromicbeadscontainaUVsensitivepigment.WhenplacedunderUVlightorsunlighttheychangefromcolourlesstocoloured.Oncethelightsourceisremovedtheircolourgraduallyfadesuntiltheyarecolourlessagain.Thereactionisreversibleandrepeatable.Thereturntothecolourlessformprovidesareactionwhichcanbesafelyinvestigatedexperimentally.ThebeadscanalsobeusedasasimpleUVradiationdetector.Manyschoolswillalreadyhaveasupplyofthesebeadsbutifnottheyareavailablefrommindsetsonline.co.ukforaround£6.50for100eitherinsinglecoloursormixed.ScientificConceptsThedyemoleculesinUVreactivebeadsconsistoftwolargeflatconjugatedsystemsorchromophoresthatareatrightanglestooneanother.TheyabsorbradiationonlyintheUVpartofthespectrumandthedyeremainscolourless.WhenUVlightexcitesthecentralcarbonatom,thetwosmallerchromophoresformonelargeconjugatedsystem.Thischromophoreislargeenoughtoshifttheabsorptionintothevisiblepartofthespectrumandthedyebecomescoloured.Bychangingthesizeofthetwoconjugatedsectionsofthemolecule,differentwavelengthsareabsorbedanddifferentdyecolourscanbeproduced.Heatfromthesurroundingsprovidestheactivationenergyneededtoreturnthecolouredformofthemoleculebacktoitslowerenergycolourlessform.

Itisthereactionthatproducesthecolourlessformthatismosteasilyinvestigatedinthisscenario.However,thereisscopeforfurtherspacerelatedwork.Starsemitawiderangeofelectromagneticradiationincludingultraviolet.OnEarthweareprotectedfrommuchofthisradiationbyouratmosphere,howeverinspaceoronotherworldstheremaybenosuchprotection.Complexorganicmoleculeswillabsorbandhencebeeffectedbythisradiation.Inmanyspaceenvironmentsmoleculesareexposedtoshortwavelengthradiationandlowtemperaturesandthisreactionprovidesamodelforthetypeofreactionsthatcanleadtotheformationoflifeprecursormoleculessuchastheaminoacidsfoundinmeteoritesandcomets.

Figure1–Pleaseseeabove

2

DescriptionofActivityAnumberofbeadsareexposedtoUVlight,eitherfromaUVlamporsunlight.IthelpstokeepthebeadscoolwhilebeingexposedtotheUV.Placingtheminabeakerwithsomecrushedicewillachievethis.Oncefullycolouredtheyarequicklyremovedfromthelightsourceandimmediatelyplacedinabeakerofwateratapre-settemperature.ThetimeforthebeadstofadetothesameshadeassomereferencebeadsnotexposedtoUVisrecorded.Thisisdoneoverarangeoftemperatures.Thebeakershouldbeplacedonawhitetileorpapertofacilitatejudgingwhenthecolourhascompletelyfaded.Atemperaturerangefrom20°Cto50°Cprovidesasuitablerangesothewatercouldcomefromhotandcoldtaps.IfaUVsourceisunavailablethenthebeadscanbestoredintheircolouredstateforseveraldaysinafreezer.

AtKeyStage4theactivitycouldbeusedtoinvestigatetheeffectoftemperatureonrateofreactionwithstudentsplottinggraphsof1/timeagainsttemperature.StudentscoulduseExceltotryandfitalinetothedataandtolinkthefindingstocollisiontheoryandtheconceptofactivationenthalpy.Alternativelytheprovidedresultssheetcouldbeusedtospeedthingsup.TeachingResourcesUVbeads,stopwatches,beakers,thermometers(0-50°Careidealbutanywilldo),whitetilesandasourceofhotandcoldwatere.g.kettleorhottap.AUVlampmaybeneededonadullwintersday.UVtorch£9.99fromAmazonUVBeadsfrom mindsetsonline.co.uk HealthandSafetyThebeadsmayrepresentachokinghazardforverysmallchildren.Careshouldbetakenwithhotwaterandglassware.AssociatedDigitalResourcesWAL_Chemistry_06_Results.docx

ExtraResources

WAL_Chemistry_06_VennDiagram_Worksheet.docx

TheVenndiagramactivityworkswellatKS4alongsidethisactivity.Itisausefuldiagnostictoolrevealingmisconceptionsinstudents(andteachers)understandingofcollisiontheory.ItcanbescaledupsoeachstudenthasanA5printoutastatementandtheVennDiagramischalkedontheground.Throughdiscussionthestudentsmustarrangethemselvesinthecorrectlocationsonthediagram.

Figure2–Pleaseseetotheleft

InvestigatingtheEffectofTemperatureontheRateofaChemicalReactionFortemperaturebetween7°Cand57°Candtimesover5s.

temp/°C temp/K time/s rate=1/time/s-1

Conclusion

QWhendoesTemp/°C=time/s?

T/K280 290 320310300 330

0.20

0.15

0.10

0

0.05

rate/s

-1

increasedconcentrationofdissolvedreactant

increasedconcentrationofdissolvedproduct

increasedsurfaceareaofsolidcatalyst

increasedtemperatureofreactants

demandthechemicalsreactfasterorelse….

givingthereactionverbalencouragement

greatervolumeofreactingsolution

usefreshlymadeupsolutions

smallerparticles(lumps)ofsolidreactant

increasedsurfaceareaofsolidreactant

presenceofsuitableenzyme

increaseconcentrationofdissolvedcatalyst

stirwell addacatalyst

useapowderinsteadofalump

buymoreexpensivechemicals

shake writetoyourMPanddemandaction

increasedpressureofgaseousreactants

increasesizeofreactionvessel

addacatalystandincreasetheconcentrationofthe

reactants

additionofsubstancethatreducesactivationenergy


carryouttheexperimentatahighertemperature

usemoreconcentratedreactants

stareatthereactioninamenacingfashion

largersurfaceareaandahighertemperature

Shinelightonthereactionmixture

Morefrequentcollisions

Greaterproportion

ofcollisions

aresuccessful

1

WeAreAliens!–Classroomactivity7(Chemistry)UsingUVReactiveBeadstofindActivationEnthalpy

OverviewTherateofachemicalreactionishighlydependentontemperature;oftena10oriseintemperaturewilldoubleareactionrate.Thechemicalreactionsthattakeplaceinlivingcellsarenowexception,indeedmanyorganismregulatetheirtemperatureveryaccuratelyforthisreason.Inthisexperimentstudentswillexplorehowratedependsontemperatureinaverydirectmannerwithoutthecomplicationofmeasuringchemicalreactantsoftheirproductsandusetheirresultstocalculatetheactivationenthalpyforthereaction

PhotochromicbeadscontainaUVsensitivepigment.WhenplacedunderUVlightorsunlighttheychangefromcolourlesstocoloured.Oncethelightsourceisremovedtheircolourgraduallyfadesuntiltheyarecolourlessagain.Thereactionisreversibleandrepeatable.Thereturntothecolourlessformprovidesareactionwhichcanbesafelyinvestigatedexperimentally.ThebeadscanalsobeusedasasimpleUVradiationdetector.Theyareavailablefrommindsetsonline.co.ukforaround£6.50for100eitherinsinglecoloursormixed.

AtKeyStage5theactivitycouldbeusedtoestablishtheactivationenergy/enthalpyforthereactionusingtheArrheniusequation.Thereactionisalsoaniceexampleofareversiblereactionwherethepositionofequilibriumcanbeshifted.ThebeadscouldbeusedtointroducetheideaofequilibriumconstantandLeChatelier’sprinciple.InvestigatingwhetherdifferentcolouredbeadshavedifferentactivationenergiescouldformthebasisofanA2chemistryinvestigation.Theresultssheetcanbeusedasisormodifiedtoprovidedifferentiation.ScientificConceptsThedyemoleculesinUVreactivebeadsconsistoftwolargeflatconjugatedsystemsorchromophoresthatareatrightanglestooneanother.TheyabsorbradiationonlyintheUVpartofthespectrumandthedyeremainscolourless.WhenUVlightexcitesthecentralcarbonatom,thetwosmallerchromophoresformonelargeconjugatedsystem.Thischromophoreislargeenoughtoshifttheabsorptionintothevisiblepartofthespectrumandthedyebecomescoloured.Bychangingthesizeofthetwoconjugatedsectionsofthemolecule,differentwavelengthsareabsorbedanddifferentdyecolourscanbeproduced.Heatfromthesurroundingsprovidestheactivationenergyneededtoreturnthecolouredformofthemoleculebacktoitslowerenergycolourlessform.

Figure01

2

Starsemitawiderangeofelectromagneticradiationincludingultraviolet.OnEarthweareprotectedfrommuchofthisradiationbyouratmosphere,howeverinspaceoronotherworldstheremaybenosuchprotection.Complexorganicmoleculeswillabsorbandhencebeeffectedbythisradiation.

Thisprovidesaspacebasedcontextforthereaction.Forexamplethepigmentmoleculesinthebeadscouldbeusedinanastronaut’seyeprotectionvisor(asinphotochromicsunglasses)withthestudentsinvestigatinghowthevisorwouldbeareeffectedbytemperature.

Inmanyspaceenvironmentsmoleculesareexposedtoshortwavelengthradiationandlowtemperaturesandthisreactionprovidesamodelforthetypeofreactionsthatcanleadtotheformationoflifeprecursormoleculessuchastheaminoacidsfoundinmeteoritesandcomets.

Thebeadsprovideaexperimentallysimplewaytoestablishtheactivationenthalpyforareaction.ThetheorybehindthisisbrieflyoutlinedbelowstartingwiththeBoltzmanndistributionofenergystates.

Forachemicalreactiontooccurreactantparticlesmustcollidewithacertainminimumkineticenergyinorderforareactiontooccur,thatis,theactivationenergy.Inacollectionofmoleculesattemperature,Tthefractionofmolecules,NhavinganenergygreaterthanEisgivenby,N=e-E/kTwherekistheBoltzmannconstant.

IfEaistheactivationenergypermoleofmolecules(i.e.inkJmol-1)theAvogadroconstant,LmustbeintroducedtocompensategivingN=e-Ea/LkT .SinceLk=R,whereRisthegasconstant,N=e-Ea/RT

Therateofthereactionwilldependonthecollisionrate(combinedwithstericfactors)andonthefractionofmoleculeswithenoughenergytoreacti.e.rate=collisionrate× fraction.SubstitutingtheexpressionforNgivestheArrheniusequation,rate=collisionrate× e-Ea/RTandtakingnaturallogsofbothsidesgives,ln(rate)=ln(collisionrate)–Ea/RTwhichcanbewrittenas

ln(rate)=–(Ea/R)× (1/T)+ln(collisionrate)Thisintheformofanequationofastraightline(y=mx+c)whereyisln(rate)andxis1/T.Thegradientis–Ea/Randtheinterceptisln(collisionrate).Soagraphofln(rate)vs1/Twillhaveagradientof–Ea/R.(R=8.31JK-1mol-1)

DescriptionofActivityAnumberofbeadsareexposedtoUVlight,eitherfromaUVlamporsunlight.IthelpstokeepthebeadscoolwhilebeingexposedtotheUV.Placingtheminabeakerwithsomecrushedicewillachievethis.Oncefullycolouredtheyarequicklyremovedfromthelightsourceandimmediatelyplacedinabeakerofwateratapre-settemperature.ThetimeforthebeadstofadetothesameshadeassomereferencebeadsnotexposedtoUVisrecorded.Thisisdoneoverarangeoftemperatures.Thebeakershouldbeplacedonawhitetileorpapertofacilitatejudgingwhenthecolourhascompletelyfaded.Atemperaturerangefrom20°Cto50°Cprovidesasuitablerangesothewatercouldcomefromhotandcoldtaps.IfaUVsourceisunavailablethenthebeadscanbestoredintheircolouredstateforseveraldaysinafreezer.

3

ln(rate)

1/T

-Ea/R

Fromthetemperaturesandtimesitispossibletocalculatetheactivationenergyforthereactionfromthegradientofagraphofln(rate)against1/temperature.Therateisjustgivenby1/timeandTisthetemperatureinK.

Thetableandgraphbelowgivetypicaltimes.Agraphofln(rate)against1/Tforthisdatahasagradientof-9908K.Sincethegradient=-Ea/RitfollowsthatEa=gradientxR(8.31JK-1mol-1)whichgivesavalueforEaof82.3kJmol-1.EainkJmol-1canalsobeestablishedfromjusttwotimes,t1andt2recordedattemperatures,T1andT2usingtheequation.

!" = 8.31 ×!" !!

!!1000× 1

!! −1!!

SampleDataforPurpleBeadsTemp/°C time/s 1/TK-1 ln(rate)

21 180 0.00340 -5.19329 70 0.00331 -4.24833 48 0.00327 -3.87136 36 0.00324 -3.58438 29 0.00322 -3.36740 24 0.00319 -3.17844 16 0.00315 -2.77345 14 0.00314 -2.63948 10 0.00312 -2.303

y=-9908x+29

-5.200

-4.700

-4.200

-3.700

-3.200

-2.700

-2.2000.00310 0.00315 0.00320 0.00325 0.00330 0.00335 0.00340 0.00345

ln(rate)

1/TK-1

4

Basedonthedatafromthetrialexperimentaboveitispossibletogenerateamathematicalmodelfortherelationshipbetweentemperatureandtime.Timeinseconds=1/(EXP((-9908/(Temperaturein°C+273))+28.51))Anextensionactivitymightbetoinvestigatedeviationsfromsuchamodel.TeachingResources

UVbeads,stopwatches,beakers,thermometers(0-50°Careidealbutanywilldo),whitetilesandasourceofhotandcoldwatere.g.kettleorhottap.AUVlampmaybeneededonadullwintersday.UVtorch£9.99fromAmazonUVBeadsfrom mindsetsonline.co.uk HealthandSafetyThebeadsmayrepresentachokinghazardforverysmallchildren.Careshouldbetakenwithhotwaterandglassware.AssociatedDigitalResourcesWAL_Chemistry_07_ChemistryOfUVReactiveBeads_Information.xlsx

Excelfilewithsampledata

WAL_Chemistry_07_ChemistryOfUVReactiveBeads_Information.pptx

PowerPointSlide

ExtraResources WAL_Chemistry_07_VennDiagram_Worksheet.docx

TheVenndiagramactivityworkswellatKS4andKS5alongsidethisactivity.Itisausefuldiagnostictoolrevealingmisconceptionsinstudents(andteachers)understandingofcollisiontheory.ItcanbescaledupsoeachstudenthasanA5printoutastatementandtheVennDiagramischalkedontheground.Throughdiscussionthestudentsmustarrangethemselvesinthecorrectlocationsonthediagram.Alsosee

PhotochromismAminoAcidsinMeteoritesComplexMoleculesinSpace

CalculatingtheActivationEnthalpyforaChemicalReactionFortemperaturebetween20°Cand50°Candtimesbetween5sand240s

temp/°C temp/K 1/temp/K-1 time/s 1/time/s-1 ln(1/time)

gradient=∆!∆! =

= ______________K Ea=gradientx-8.31Jmol-1K-1=_______________kJmol-1

QWhendoesTemp/°C=time/s?

1/T/10-3K3.0 3.1 3.43.33.2 3.5

-1.5

-2.5

-3.5

-5.5

-4.5

ln(1/tim

e)

1

increasedconcentrationofdissolvedreactant

increasedconcentrationofdissolvedproduct

increasedsurfaceareaofsolidcatalyst

increasedtemperatureofreactants

demandthechemicalsreactfasterorelse….

givingthereactionverbalencouragement

greatervolumeofreactingsolution

usefreshlymadeupsolutions

smallerparticles(lumps)ofsolidreactant


presenceofsuitableenzyme

increaseconcentrationofdissolvedcatalyst

stirwell addacatalyst

useapowderinsteadofalump

buymoreexpensivechemicals

shake writetoyourMPanddemandaction

2

increasedpressureofgaseousreactants

increasesizeofreactionvessel

addacatalystandincreasetheconcentrationofthe

reactants

additionofsubstancethatreducesactivationenergy


carryouttheexperimentatahighertemperature

usemoreconcentratedreactants

stareatthereactioninamenacingfashion

largersurfaceareaandahighertemperature

Shinelightonthereactionmixture

Morefrequentcollisions

Greaterproportionofcollisions

aresuccessful

1

WeAreAliens!–Classroomactivity8(Chemistry)Couldlifeexistinthisicecore?Answersheet

NotalllifeonEarthrespiresaerobicallyusingglucoseasanenergysource.Therearemanytypesof

bacteriathatrespireusinginorganicmoleculeseitherwithorwithoutoxygen.Herearesome

examples.

1. Theequationbelowshowsarespiration(redox)reactioncarriedoutbysocallediron

bacteria.

H2O+Fe2O3→2Fe(OH)2+O2

water+iron(III)oxide→iron(II)hydroxide+oxygen

a. GivetheoxidationstateoftheironinFe2O3 +3

andFe(OH)2 +2

b. GivetheoxidationstateoftheoxygeninH2O -2

andO20

c. Whatisactingasthereducingagent? water

2. Thepurplesulfurbacteriaareoftenfoundinhotspringsorstagnantwater.Unlikeplants

theydonotusewaterastheirreducingagent,andsodonotproduceoxygen.Insteadthey

usehydrogensulfide,whichisoxidizedtoproducegranulesofelementalsulfur.Thisinturn

maybeoxidizedtoformsulfuricacid.Thesebacteriathriveissulphuricacidlakes.

a. Bybalancinghydrogenwithhydrogenions,writeanelectricallybalancedequationforthe

oxidationofhydrogensulphide(H2S)toelementalsulphur

H2Sà2H++S+2e

-

b. Explainwhythisreactionisoxidation

Hydrogenhasbeenremoved,oxidationstateofsulphurhasincreasedfrom-2to0

3. Biologicalnitrogenfixationoccurswhenatmosphericnitrogenisconvertedtoammoniaby

anenzymecallednitrogenaseThereactionis:

N2+8H++8e

−→2NH3+H2

a. Explainwhythisisaredoxreactionandnametheoxidisingagent

Nitrogenisoxidisedfrom0to+3,hydrogenisreducedfrom+1to0sobothreductionand

oxidationhavetakenplace.Theoxidisingagentishydrogen.

Sowhatdoyouthink,couldlifeexistonEuropaorEnceladus?

Howmuchwouldyoubepreparedforgovernmentstospendinordertofindout?

1

WeAreAliens!–Classroomactivity8(Chemistry)IceCoreAnalysisOnEarth,whereverthere’swaterthere’slife,evenifmuchofthatwaterisfrozen.Ourownsolarsystemcontains

anumberofsuchenvironments,whichastrobiologistsarekeentoexplore.Inthisactivitystudentswillanalyseice

coresthathavecomefromfrozenworldssuchasEuropa,oneofJupiter’smoonsandEnceladus,amoonof

Saturn.TheaccompanyingPowerPointwithpicturesofthesemoonscouldbeusedtofurthersetthescene.

Thecompositionoftheicecorecanbemodifiedtomatchparticularspecificationsortomatchtheresources

availableindifferentschools.Thedetailsprovidedinthisactivityarespeculativeandarenotintendedto

accuratelyrepresentthecompositionofparticularmoons!

ChemistryCoveredAnintroductiontoinorganiccompoundsincludingtheformulaeofnaturallyoccurringcompounds.

Acids,basesandneutralisationreactionsincludingacid-basetitrations.

Oxidationstatesandredoxreactionsincludingaredoxtitration.

OutlineofPracticalActivityStudentsaregivensamplesoficepurportedtobefromEnceladus/Europaonwhichtheycarryoutthefollowing

activitiesoverasequenceoflessons:

• Meltthesample,recordthevolumeandfilterit.

• Examinethesolidsrecoveredusingalowpowermicroscopyandidentifymineralspresent.

• Performqualitativetestsonthemeltwatertodiscovertheidentityofdissolvedions.

• Titrateaknownvolumeofthemeltwateragainstsodiumhydroxidetocalculatetheconcentrationofthe

acidpresent.

• Titrateaknownvolumeofthemeltwateragainstmanganate(VII)ionstodeterminetheconcentrationof

iron(II)

MakingtheIceCoresMakeupasolutionofapproximately0.05moldm

-3iron(II)sulphateinapproximately1moldm

-3sulphuricacid.To

thisbaseaddaselectionofmineralfragments,producedbysmashingupcheapmineralsampleswithahammer.

Tomakethecores,usethecylindricalicetraysnowreadilyavailableforcoolingdrinksbottles.(suitabletrayhere

atAmazonfor£3.50)Ensurethateachcorecontainssomeofthemineralfragments.Alternatively,makeupa

largeblockoficeusingalargeice-creamcontainerorsimilarandprovidestudentswithsamplesoficeobtained

bysmashingthelargeblockwithahammer.Itispossibletogetthemineralfragmentsdistributedthroughoutthe

icecoresbymakingupthecoresfromcrushedfrozensolutionandicecoldsolution.Thiswillpreventthemineral

grainsfromsinking.

Ifdesired,addothersaltsolutionsforstudentstoperformqualitativeanalysison.

Onlyverysmallamountsofmineralsamplesarerequiredastheywillbeviewedusingamicroscope.Youmay

wishtomixthefragmentsyouobtainwithfinesand(amineralitself)tomakethemeasiertohandle.

Mineralsamplessuitableforthiscanbeobtainedcheaply(95peach)fromukge.co.uk/uk/small-minerals.asp

Itisrecommendedthatyouobtainarangeof5or6minerals,ideallyalldifferentcolourstoaididentification.

Suitablemineralsinclude:

• Pyrite

• Malachite

• Quartz

• Galena

• Amethyst

• Chrysocolla

Studentswillneedabout30-40cm3ofsolution(about4standardicecubes)

2

RiskAssessmentWhenworkingwithicecubespreviouslystudentsmayhavetriedtodropthemdownthenecksofotherstudents.Theyshouldbewarnedthattheseare“acid”cubesandshouldbenotbehandled.1moldm-3sulphuricacid irritant0.05moldm-3iron(II)sulphate lowhazardMineralsamples lowhazardwhenhandledinthisformbutgalenaistoxicand,asa

precaution,studentsshouldwashtheirhandsbeforeleavingthelab.0.1moldm-3sodiumhydroxidesolution irritant1moldm-3hydrochloricacid irritant0.2moldm-3silvernitrate irritant0.5moldm-3bariumchloride harmfulUniversalindicator flammablePhenolphthaleinindicator flammable0.001moldm-3potassiummanganate(VII)lowhazard

EquipmentListRecordingandMineralIdentification

• Beakers• CylindricalicecubetraysORandcontainertomakealargeblockofice• Accesstofreezer• Iron(II)sulphate• 1moldm-3sulphuricacid• Crushedmineralsamples(seebelow)• Lowpowermicroscopes(oftenthoseusedatKS3/4aremostsuitable)• Filterpaperandfunnels

QualitativeAnalysis

• Meltedicesamplefrompreviouswork• Qualitativeanalysisinformationsheet• Universalindicator• Rangeofchemicalswithwhichtocarryoutqualitativeanalysis

o 0.1moldm-3sodiumhydroxidesolutiono 0.5moldm-3hydrochloricacido 0.2moldm-3silvernitratesolutiono 0.5moldm-3bariumchloridesolutiono spills

Acid-BaseTitration

• meltedicesamplefrompreviouswork• 100cm3volumetricflask• Distilledwater• 10cm3pipette• 25cm3pipette• Burette,burettestandandclamp• Phenolphthaleinindicator• Whitetile• Funnel• 0.10moldm-3sodiumhydroxidesolution(madeupaccurately)

RedoxTitrationAsabovebutwithoutindicatorandpotassiummanganatereplacessodiumhydroxide

• 0.001moldm-3potassiummanganate(VII)solution(madeupaccurately)

3

StudentPracticalWork1. RecordingandMineralIdentificationThisisalovelyactivitythatstudentsoftenreallyenjoy.Usingamicroscopetoviewsmallmineralsamplesiscomparabletoviewinglargemineralsampleswiththenakedeye.Mostwillfindthesamplestheyviewbeautifulandwillbekeentoidentifythem.a. Placetheicesampleinaclean,drybeakeranduseaBunsenburnertomelttheice.b. Filteryourmeltedsamplecollectingthefiltrateinameasuringcylinder(choosethemostappropriatesize

available).Makesurethatallthesolidendsupbeingtransferredtothefilterpaper.c. Recordthevolumeofsolutionyouobtain.Transferyoursolutiontothecontaineritwillbestoredinandlabel

itclearly.Youwillneeditagainlater.d. Examinethecontentsofthefilterpaperwithamicroscopeusingalowpowerlens.e. Usethemineralidentificationsheettotryandidentifythemineralsamplesyoufind.2. QualitativeAnalysisYoumaywishtoadaptthispartoftheanalysistomatchyourownspecificationornottocarryoutthispartofthepracticalatall.

Studentsareprovidedwithaninformationsheetthatdetailsarangeofqualitativeanalyticaltests.Theirtaskistocarryoutthetests,decidewhichionsarepresentandsuggesttheformulaeofsomedissolvedsaltswhichmaybepresent.

TheyshouldalsouseuniversalindicatortofindthepHofthesolution.Warnstudentstoonlyusesmallamountsoftheirsolution.Theyshouldleaveatleast20cm3forfurtheranalyticalwork.3. Acid–BaseTitration

Thisisastandardacid-basetitrationsetinanovelcontext.Theendpointofthetitrationisthefirstpermanentappearanceofpink.

a. Usinga10cm3pipette,transfer10.00cm3ofyoursampleintoa100cm3volumetricflask.b. Usingdistilledwater,makethesolutionuptothemarkandshakewell.Younowhavea1in10dilutionofyour

originalsample.c. Usingapipettetransfer20/25cm3ofyoursampleintoaconicalflaskandaddafewdropsofphenolphthalein

indicator.d. Setupaburetteandfillitwith0.10moldm-3sodiumhydroxidesolution.e. Carryoutthetitrationuntilyouhaveatleasttwoconcordantresults.4. RedoxTitrationManganate(VII)ionsareusedheretodeterminetheconcentrationofiron(II)ionspresentintheicecore.Manganate(VII)isaddedtothesamplefromaburetteandisdecolourisedimmediately.Assoonasallthereducingagent(Fe2+ions)isusedup,thesolutionintheconicalflaskgoespalepinkduetothepresenceofMnO4

-ions.Theendpointofthetitrationisthefirstpermanentappearanceofthispalepinkcolour.Noindicatorisrequiredasthemanganate(VII)isself-indicating.

a. Usinga10cm3pipette,transfer10.00cm3ofyoursampleintoa100cm3volumetricflask.b. Usingdistilledwater,makethesolutionuptothemarkandshakewell. Younowhavea1in10dilutionofyouroriginalsample.c. Usingapipettetransfer20/25cm3ofyoursampleintoaconicalflask.d. Setupaburetteandfillitwith0.001moldm-3potassiummanganate(VII)solution.e. Carryoutthetitrationuntilyouhaveatleasttwoconcordantresults.

1

WeAreAliens!–Classroomactivity8(Chemistry)IceCoreAnalysis

1. MineralIdentification

a. Placetheicesampleinaclean,drybeakeranduseaBunsenburnertomelttheice.b. Filteryourmeltedsamplecollectingthefiltrateinameasuringcylinder(choosethemost appropriatesizeavailable).Makesurethatallthesolidendsupbeingtransferredtothefilterpaper.c. Recordthevolumeofsolutionyouobtain.Transferyoursolutiontothecontaineritwillbestoredin andlabelitclearly.Youwillneeditagainlater.d. Examinethecontentsofthefilterpaperwithamicroscopeusingalowpowerlense. Usethemineralidentificationsheettotryandidentifythemineralsamplesyoufind.

Volumeofsolution cm3

Briefdescriptionincludingcolour Possiblename Possibleformula

2. QualitativeAnalysis

Usetheinformationsheetstocarryouttestsonyousampleofmeltwater.Makesureyoukeepatleast20cm3ofsampleforthenexttwoexperiments.Usethesetablestorecordyourpositiveresults

CationsPresent AnionsPresent

ColourwithUniversalIndicator EstimatedpH

2

Usingyourqualitativeanalysisresults:

Suggestwhatacidcouldbepresent Suggesttheformulaofsomepossibledissolvedsalts

3. Acid–BaseTitration

Youareusingsodiumhydroxideofknownconcentration(intheburette)tofindouttheconcentrationofacidinyouricesample.Theendpointofthetitrationisthefirstpermanentappearanceofpink.a. Usinga10cm3pipette,transfer10.00cm3ofyoursampleintoa100cm3volumetricflask.b. Usingdistilledwater,makethesolutionuptothemarkandshakewell.Younowhavea1in10dilutionofyouroriginalsamplec. Usingapipettetransfer20/25cm3ofyoursampleintoaconicalflaskandaddafewdropsof phenolphthaleinindicatord. Setupaburetteandfillitwith0.10moldm-3sodiumhydroxidesolutione. Carryoutthetitrationuntilyouhaveatleasttwoconcordantresults

Titre/cm3Rough 1 2 3 mean

Yourmeltwatersamplecontainssulphuricacid(H2SO4).Inthistitration,itwasneutralisedbysodiumhydroxidesolution.i. Writeabalancedequationfortheneutralisation

ii. Youused0.10moldm-3sodiumhydroxidesolution.Useyourtitremeantocalculatethenumberofmolesofsodiumhydroxideyouadded.

iii. Useyourequationfromitoworkoutthenumberofmolesofsulphuricacidthatmusthavebeenpresentintheconicalflask.

iv. Youhadeither20or25cm3ofacidinyourconicalflaskatthestartofthetitration.Useyouranswer fromiii.tocalculatetheconcentrationofthesulphuricacidpresent

v. Thesolutionintheconicalflaskwasa1in10dilutionofyourmeltwater.Calculatetheconcentrationofsulphuricacidintheoriginalice.

3

4. RedoxTitration

Inthistitrationpurplemanganate(VII)ionsareusedtodeterminetheconcentrationofiron(II)ionspresentintheicecore.Manganate(VII)isaddedtothesamplefromaburetteandisdecolourisedimmediately.Assoonasallthereducingagent(Fe2+ions)isusedup,thesolutionintheconicalflaskgoespalepinkduetothepresenceofMnO4

-ions.Theendpointofthetitrationisthefirstpermanentappearanceofthispalepinkcolour.Noindicatorisrequiredasthemanganite(VII)isself-indicating.a. Usinga10cm3pipette,transfer10.00cm3ofyoursampleintoa100cm3volumetricflask.b. Usingdistilledwater,makethesolutionuptothemarkandshakewell.Younowhavea1in10dilutionofyouroriginalsample.c. Usingapipettetransfer20/25cm3ofyoursampleintoaconicalflask.d. Setupaburetteandfillitwith0.001moldm-3potassiummanganate(VII)solution.e. Carryoutthetitrationuntilyouhaveatleasttwoconcordantresults.

Titre/cm3Rough 1 2 3 mean

YourmeltwatersamplecontainedFe2+ionswhichreactedwithMnO4

-ions.Theequationforthereactionisbelow.

8H++5Fe2++MnO4-à4H2O+5Fe3++Mn2+

i. Usetheequationtotellyouwhichelementwasoxidised. Givethebeforeandafteroxidationstatesforthiselement.

ii. Whichelementwasreduced?Givethebeforeandafteroxidationstatesforthiselement.

iii. Youadded0.001moldm-3potassiummanganate(VII)(KMnO4)solutiontotheflask. Useyourtitretocalculatethemeannumberofmolesofmanganateionsadded.

iv. Usetheequationgivenabovetoworkoutthenumberofmolesofiron(II)thatthemanganitereactedwith.

v. Youhadeither20or25cm3ofironsolutioninyourconicalflaskatthestartofthetitration. UseyouranswerfromivtocalculatetheconcentrationoftheFe2+present.

vi. Thesolutioninyourconicalflaskwasa1in10dilutionfromyourmeltwater. Calculatetheconcentrationofironintheoriginalice.

4

Couldlifeexistinthisicecore?

NotalllifeonEarthrespiresaerobicallyusingglucoseasanenergysource.Therearemanytypesofbacteriathatrespireusinginorganicmoleculeseitherwithorwithoutoxygen.Herearesomeexamples.1. Theequationbelowshowsarespiration(redox)reactioncarriedoutbysocalledironbacteria. H2O+Fe2O3→2Fe(OH)2+O2 water+iron(III)oxide→iron(II)hydroxide+oxygena. GivetheoxidationstateoftheironinFe2O3andFe(OH)2

b. GivetheoxidationstateoftheoxygeninH2OandO2c. Whatisactingasthereducingagent?2. Purplesulphurbacteriaareoftenfoundinhotspringsorstagnantwater.Unlikeplantstheydonotusewater

astheirreducingagent,andsodonotproduceoxygen.Insteadtheyusehydrogensulphide,whichisoxidizedtoproducegranulesofelementalsulphur.Thisinturnmaybeoxidizedtoformsulphuricacid.Thesebacteriathriveissulphuricacidlakes.

a. Bybalancinghydrogenwithhydrogenions,writeanelectricallybalancedequationfortheoxidationofhydrogensulphide(H2S)toelementalsulphur.b. Explainwhythisreactionisoxidation.

3. Biologicalnitrogenfixationoccurswhenatmosphericnitrogenisconvertedtoammoniabyanenzymecallednitrogenase.Thereactionis: N2+8H++8e−→2NH3+H2 Explainwhythisisaredoxreactionandnametheoxidisingagent.Sowhatdoyouthink,couldlifeexistonEuropaorEnceladus?Howmuchwouldyoubepreparedforgovernmentstospendinordertofindout?

WeAreAliens!–Classroomactivity8(Chemistry)-Mineral Information

Turquenite Blacktourmaline Pyrite Sodalite Tigereye Galena Malachitecalciumborosilicate

hydroxide acomplexsilicate ironsulphide sodiumaluminiumsilicate

silicondioxidewithtracesofiron leadsulphide coppercarbonate

hydroxideCa2B5SiO9(OH)5 (Ca,K,Na,)

(Al,Fe,Li,Mg,Mn)3(Al,Cr,Fe,V)6(BO3)3(Si,Al,B)6O18(OH,F)4

FeS2 (Na4Al3(SiO4)3Cl) SiO2 PbS Cu2CO3(OH)2

Amethyst Calcite Rosequartz Quartz Rhodonite Chrysocollasilicondioxidewithtracesoftitaniumor

manganesecalciumcarbonate

silicondioxidewithtracesoftitaniumor

manganesesilicondioxide manganesesilicate copperandaluminiumsilicate

SiO2 CaCO3 SiO2 SiO2 MnSiO3 (Cu,Al)2H2Si2O5(OH)4·nH2O

TestsforAnionsAnion Symbol Test Positiveresult

Bromide Br- Addsilvernitratesolution

Paleyellowprecipitateformswhichdissolvesslightlyinammoniasolution.

Carbonate CO32- Adddilute

hydrochloricacidEffervescence(fizzing)isseenandcarbondioxideisgivenoff

Chloride Cl- Addsilvernitratesolution

Thickwhiteprecipitateformswhichdissolvesinammoniasolution.

Iodide I- Addsilvernitratesolution

Paleyellowprecipitateformswhichdoesnotdissolveinammoniasolution.

Sulphate SO42- Addbariumchloride

solution. Whiteprecipitateforms.

TestsforCationsSodiumhydroxidetestCation Formula ObservationsAluminium Al3+ Whiteprecipitatewhichdissolveswhenmoresodium

hydroxideisaddedCalcium Ca2+ Whiteprecipitatewhichdoesnotdissolvewhenmore

sodiumhydroxideisaddedMagnesium Mg2+ Whiteprecipitatewhichdoesnotdissolvewhenmore

sodiumhydroxideisaddedCopper Cu2+ BlueprecipitateIron(II) Fe2+ GreenprecipitateIron(III) Fe3+ Brown(rust)precipitateLithium Li+ NoprecipitateSodium Na+ NoprecipitatePotassium K+ NoprecipitateAmmonium NH4

+ Noprecipitate

Flametest:SoakaspillinthesolutiontobetestedandplacethespillintheblueflameofaBunsenburnerCation Formula FlamecolourLithium Li+ RedSodium Na+ OrangePotassium K+ LilacCalcium Ca2+ BrickredBarium Ba2+ LightgreenCopper Cu2+ Blue-green

TestsforAnionsAnion Symbol Test Positiveresult

Bromide Br- Addsilvernitratesolution

Paleyellowprecipitateformswhichdissolvesslightlyinammoniasolution.

Carbonate CO32- Adddilute

hydrochloricacidEffervescence(fizzing)isseenandcarbondioxideisgivenoff

Chloride Cl- Addsilvernitratesolution

Thickwhiteprecipitateformswhichdissolvesinammoniasolution.

Iodide I- Addsilvernitratesolution

Paleyellowprecipitateformswhichdoesnotdissolveinammoniasolution.

Sulphate SO42- Addbariumchloride

solution. Whiteprecipitateforms.

TestsforCationsSodiumhydroxidetestCation Formula ObservationsAluminium Al3+ Whiteprecipitatewhichdissolveswhenmoresodium

hydroxideisaddedCalcium Ca2+ Whiteprecipitatewhichdoesnotdissolvewhenmore

sodiumhydroxideisaddedMagnesium Mg2+ Whiteprecipitatewhichdoesnotdissolvewhenmore

sodiumhydroxideisaddedCopper Cu2+ BlueprecipitateIron(II) Fe2+ GreenprecipitateIron(III) Fe3+ Brown(rust)precipitateLithium Li+ NoprecipitateSodium Na+ NoprecipitatePotassium K+ NoprecipitateAmmonium NH4

+ Noprecipitate

Flametest:SoakaspillinthesolutiontobetestedandplacethespillintheblueflameofaBunsenburnerCation Formula FlamecolourLithium Li+ RedSodium Na+ OrangePotassium K+ LilacCalcium Ca2+ BrickredBarium Ba2+ LightgreenCopper Cu2+ Blue-green

1

WeAreAliens!–Classroomactivity1(Physics)The“boilingwaterinasyringewithoutheatingit”experimentandwhyoceanscan’texiston

Marsnow–butonceuponatime,theydid!

Boilingisthelarge-scaleevaporationofaliquidintothegaseousstateand,forpurewater,

occursat100oCat1atmosphericpressure(1013.25mbor101325Pa).

Asatmosphericpressuredecreases,thetemperatureatwhichboilingoccursalsoreduces:

Figure01

Asweascendintheatmospherethedecreasingairpressuremeansthatwaterboilsat

progressivelylowertemperatures.

OnthesummitofMountEverest,whichis8,848m(29,028ft)abovesealevel-onlyslightly

lowerthanthealtitudecommercialairlinersflyat-thisfigurehasreducedfromourfamiliar

100Centigradetoaround70degreesCentigrade.

Higherstill,theconsequencesforunprotectedhumansbecomeevenmoreinsidious.At

20,000m(63,000ft)theboilingpointofwaterequalsahuman'sbodytemperature:37

degreesCentigrade.Ifweconsiderthemainconstituentofthehumanbody,therelevance

ofthisparticularpressuretohumanphysiologyandsurvivalisclear.Infact,theaeromedical

boundaryofspaceistakenasbeingatthisaltitude(63000ft),sinceafullpressuresuit

wouldbeneededforsurvival.Thepressureissolow(6%ofsea-level)thattheboilingpoint

ofwaterisbelowtheaveragehumanbloodtemperature.Theoutsidepressureislessthan

thepartialpressureofwaterinthebody.

Acommonmisconceptionisthatanunprotectedhuman'sbloodwouldstartboilinginthe

arteriesandveins,butsincetheskinisareasonablygoodpressurevesselthiswouldnotbe

thecase.

However,thedramaticoutgassingofnitrogendissolvedinthebloodstream(similarto,but

farmorerapidthantheexperiencesofdiverswhoascendtooquicklyfromdepth)coupled

withtheeffectsofexplosivedecompressionandlackofoxygenwouldresultin

unconsciousnessinseconds,anddeathwithinaminuteortwo.

2

Fromanaeromedical,orhumanphysiologyandsurvivalperspective,thisistheboundaryof

space

Martianmeandatumpressureiswellbelowthepressureequivalentatthisaltitude,and

thusafull-pressuresuitlikethosecurrentlyinuseforspacewalks(EVAs)ontheInternational

SpaceStationwouldbeneeded.

CurrentsurfaceconditionsonMarsandliquidwater

Figure2(aboveleft)Figure3(aboveright)

Atpresent,ambientpressuresaresolowthatliquidwaterpouredoutontotheMartian

surfacewouldsimultaneouslyfreezeandevaporateaway.Therearenolong-lyingareasof

liquidwateranywhereonthecurrentsurface.

Yetweseemuchevidenceofawarmer,wetterpast–whatlookslikeanancientriversystem

belowspansseveralhundredkilometres:

Figure4

Left:afrozenMartianlake?

Below:Sedimentaryrocks

photographedbyOpportunity

3

Mars–aburiedocean?

MarsOdyssey,whichhasbeenorbitingMarssinceOctober2001carriedaneutronspectrometertomeasuretheneutronfluxproducedduetothefollowing:

• High-energygalacticcosmicradiation(GCR)slamsintotheMartiansurface–

neutronsareejectedfromsurfaceatomicnuclei

• Someoftheejectedneutronfluxisupwardstowardstheorbitingspacecraftwhich

detectsthem

• Eachchemicalelementcreatesitsownuniquedistributionofneutronenergies

• Themeasuredneutronflux“signatures”allowdeterminationofthetopsurface

material’schemicalcomposition

• Hydrogeninthesoil(assumedtobeinsubsurfaceice)willeffectivelyabsorb

neutronenergyandreducetheneutronfluxthatescapesfromthesurfacetobe

detectedonorbit.

• Additiongammafluxescausedbynuclearde-excitationafterGCRinteractionswith

surfacenucleiwerealsomeasuredbythespacecraft

Thefollowingmapshowstheinferreddistributionofsubsurfaceicefromorbitaldata:

Figure5(below)

Thisdatasetisvalidforsurfacedepthsofonly1morthereabouts–yettheamountofwater

indicatedisstaggering.

MorerecentresultsfromNASA’sMarsPhoenixlanderhaveconfirmedthepresenceof

subsurfaceicewhichslowlysublimatesonexposuretosurfaceconditions.

4

Conclusion

AtpresenttheconditionsonthesurfaceofMarsaresuchthatcomplexEarthorganisms

suchasourselveswouldfinditimpossibletosurvivewithoutsignificantprotectionfromthe

extremeenvironmentalparametershighlightedinthedemonstrationfilms.

Yetallthegeologicalandobservationalevidencepointstoaplanetthatwasonce

significantlywetterandwarmer.AllovertheMartiansurfaceweseeevidenceoffeatures

associatedwithlong-standingextensivebodiesofliquidwater…..dendriticriversystems,

evidenceofcatastrophicfloodeventsandrocksthatrequirethepresenceofliquidwaterto

form.Theseimplytheplanetoncehadamuchdenseratmosphere,onethatwouldasa

consequencehavehadsignificantlyhighertemperaturesthanthosecurrentlyextant.What

happened?

Figure6(above)

Figure7(above)

Marstoday.ThisMGScompositeimageis

centredonVallisMarineris,thegiant

tectoniccrackinMars’crust.Atleftcanbe

seentheTharsisbulgewiththe

“supervolcanoes”Arsia,Pavonisand

AscraeusMons.

Thisartisticimpressionshows

whatMarsmayhavelookedlike

3.8-3.5billionyearsago(Noachian

epoch).TheNorthernhemisphere

lowlandsarecoveredbyashallow

oceanthatfillsVallisMarineris.

5

ImageReferencing:

Figure01-CHEM.PURDUE.EDU(dateunknown)Boiling;Factorsthataffectboilingpoint[WWW]PurdueeduAvailablefrom:http://www.chem.purdue.edu/gchelp/liquids/boil.html

[06/12/2012]

Figure02-VIRGINIA.EDU(2012)WateronMars:FrozenLakeinCrater[WWW]Credit:

ESA/DLR/FUBerlin(G.Neukum)

http://www.astro.virginia.edu/class/oconnell/astr121/im/ice-in-crater-Mexpress-lg.jpg

[06/12/2012]

Figure03-NASA(2012)MarsExplorationProgramAnalysisGroup(MEPAG)[WWW]Pancam

photomosaic,approximatelytruecolor:NASA/JPL/CornellAvailablefrom:

http://mepag.nasa.gov/science/1_ancient_persistent_liquid_water/index.html

[06/12/2012]

Figure04-ABOVETOPSECRET(2011)TheSearchForLife.Part2–Aretheyhere?[WWW]

Availablefrom:http://www.abovetopsecret.com/forum/thread669103/pg1[06/12/2012]

Figure05-NASA(2012)MarsExplorationProgramAnalysisGroup(MEPAG)[WWW]

Graphic:NASA/JPL/UniversityofArizonaAvailablefrom:

http://mepag.nasa.gov/science/3_Modern_Water/index.html[06/12/2012]

Figure06-NRAO(2012)Mars[WWW]Availablefrom:

http://www.gb.nrao.edu/epo/sol_sys/mars.html[06/12/2012]

Figure07-CARROLL,MICHAEL(2012)LiquidWateronMars(artisticimpression)[WWW]

PaintingbyMichaelCarrollAvailablefrom:

http://www.lpi.usra.edu/publications/slidesets/redplanet2/slide_28.html[06/12/2012]

1

WeAreAliens!–Classroomactivity2(Physics)COMETRECIPE

CometIngredientsWaterinajug(abouthalftheamountofdryice)

Binliners

DryIce(about2-3x600mlcontainerfulls)

1Spoonfulofsand1Spoonfulofcarbondust

Fewdashesofworcestersauce(organiccomponent)

Fewdashesofwhisky/redwine(optional–themethanol/ethanolcomponent)

BowlDisposalBucket

RubberGlovesWoodenSpoon

ClearscreenPolysterenecontainerfordryice

Method

1. Takeabinlineranduseittolinethebowl.

2. Addtheingredientsofyourcomet–water,sand,carbondust,worcestersauce.These

replicatethecompoundsthatrealcometsarecomposedof.Volunteersoftheaudience

canaddsomeofthese.Mixwellwithwoodenspoon.

Anoteonthesignificanceoftheingredients:

§ WATER - how comets have large amounts ofH2O, and in the past it is believed

comets could have brought water to Earth through impacts with our planet

billionsofyearsago.§ The SAND, TheCARBON,ALCOHOL, and theWORCESTER SAUCE for the organic

component.Cometshaveall theright ingredients for life,but themixture isnot

underthecorrectconditionsforlifetoexist.§ THE DRY ICE – frozen CO2, the frozen gas that holds together our comet and

sublimateswhenitinteractswiththesolarwindandsolarradiationtoformthe

comaandgastail.

3. Finallyaddthedryice.Wearingglovesfeelaroundthebinlinerandmouldthecomet

intoonelump.Don’tcompressittoohardasthecometmaybreak,allowsteamgasto

escape.

4. Whenthedemonstrationiscompletedplacethecometsinsidethebinlinerinabucket.

2

SafetyPrecautions

• Whenhandlingthedryicewearglovesandgoggles.Donottouch,swallowortastethedryice.Donotallowstudentstoonearthedryice.Givetheaudienceclearinstructionsonthehazardandthedistancetheyshouldbeseatedformthedryiceasthecometmay‘spit’

• Donotsealthedryiceintoacontainerasexplosiveoutgassingmayresult!• Transportdryiceinaplasticbaginsideabox.• Disposeofcometoutsideinawell-ventilatedareawherestudentscan’taccessit.

TheScience

DryiceisfrozenCarbonDioxide(-78.5oC,or-109.3oF),orCO2,whichisagasunderstandardtemperatureandpressure conditions. Theatmosphere contains about0.035%of this gas.CO2isagreenhousegas,whichmeansitabsorbslightatinfraredwavelengths.Anincreasein the concentration of this gas may cause an increase in the atmosphere's averagetemperature.ThehighconcentrationofCO2(>96%)intheatmosphereoftheplanetVenuscontributestothatplanet'shighaveragetemperature.

At normal atmospheric pressureon this planet, frozenCO2doesn'tmelt into a liquid, butratherevaporatesdirectly into itsgaseous form -hence thename ‘dry ice’. Thisprocess iscalledsublimationandisresponsiblefortheformationofacomet’scoma.WecanseeCO2gassublimingawayfromourcometfromwherewatervapourintheaircondensesaroundit.

1

WeAreAliens!–Classroomactivity3(Physics)Pressureandwhatit’sreallylikeonEarth,VenusandMars!

WhatdoweMeanbyPressure?

Putsimply,pressureisthemeasureofaforcespreadoverasurfacearea.Theunitof

pressure,thePascal,istheforceof1Nactingoveranareaof1squaremetre.

TheOriginofAtmosphericPressureAtmosphericpressure,whichwetakeforgranted,canhave

unusualeffects,asweseeintheglassofwaterandcard

experiment.Itscauseissimplytheweightofatmosphereabove

uswhichextendstoanaltitudeofwellover100km-the

internationallyacceptedboundaryofspace(althoughnearly

90%ofthetotalmassoftheatmosphereiswithin10kmofthe

Earth’ssurface).

Wetendtoforgetthatwearelivingatthebottomofan

“ocean”ofair.

Figure01

Atmosphericpressurevariesatagivenlocationwiththepassageofweathersystems,and

decreasesexponentiallywithaltitude.Thestandardvalueis101.325Pa(1013.25mb),also

knownas1atmosphere(atm).ThismeansthateverysquaremeteroftheEarth’ssurfaceis

sittingunder10tonnesofatmosphericmass!

Figure02–Shownabove

2

TheEffectsofAtmosphericPressureGaspressureiscausedbymomentumchangesduringthecollisionsbetweenthemoleculesoratomsthatcomposethegas,andanythingthathappenstobeintheway!Weoftenmodelthebehaviourofgasesbyconsideringthemtobe“ideal”gases.Thesearemonatomicgaseswithatotalparticlevolumewhichisnegligibleincomparisontothetotalvolumeoccupiedbythegasandwithnointerparticleinteractionsapartfromduringcollisions.TheIdealGasEquation–GCSE+levelThisisderivedbyputtingtogetherthefamiliarequationsfromthreeLawspV=constant,p/T=constantandV/T=constantforaconstantmassofidealgas;whichleadsto(ALevel)n=numberofMOLESofthegas(oneMOLEisdefinedasbeingAvogadro’snumberofsomething.Ifyouevergetstressedaboutwhatamoleis,justthinkofitasbeing6.02x1023ofsomething–beitgasmoleculesorpeople!)R=MOLARGASCONSTANT–ameasureofthekineticenergy/temperaturelinkforonemole’sworthofmolecules/particles.T=AbsolutetemperatureinKelvinForaMICROSCOPICratherthanMACROSCOPICmodel(i.e.consideringthesmallnatureofparticlesratherthanmassesofthematonce),theidealgasequationisoftenwrittenasBoltzmann’sconstantgivesusadirectlinkbetweentranslationalkineticenergyand

temperatureforasingleparticle.Themeantranslationalkineticenergyofaparticleina

2

22

1

11

TVp

TVp

=

nRTpV =

N = total absolute number of particles (rather than grouping them into moles) T = temperature in K

k = BOLTZMANN’s CONSTANT = 1.38*10-23 J/K

NkTpV =

3

systemattemperatureTis3/2kT.(Ifwestartconsideringother“degreesoffreedom”suchasmolecularROTATIONorVIBRATION,thenweaddafactorofkT/2foreachextradegreeandmodethat’sincluded.)PressureandAltitude(GCSEandALevel)Asweascendintheatmosphere,theairpressurediminishes,asthereislessweightofairabove.ALevelmodellingIfweassumeanidealgasisbehavingHYDROSTATICALLY,thenforaparticularlayerofgasatagivenaltitudethedownwardforceofitsweightandthedownwardforceexertedbypressureinthelayeraboveisequaltotheupwardforceexertedbypressureinthelayerbelow.It’spossibletoshowthatthefollowingrelationholds

ForEarth,withanapproximateatmosphericcompositionof80%N2and20%O2,wefindameanmolarmassof28.8g(N2=28,O2=32)whichneedstobeexpressedinkg.TheEarthvaluetranslatestoameanmolecularMASSof28.8timesthatofahydrogenatom=4.8x10-26kg.UsingthisequationisasstraightforwardasthemorefamiliarusesofexponentialswithregardstoTakingthesea-levelvalueforpressuregivenabove,ameanatmospherictemperatureof0oCandtheheightofMountEverestas8850m,wecanshowthatthepressureonitssummitisaboutone-thirdofthesea-levelvalue,andcalculateitinPascals.OfcoursethemodelisinaccurateinthatitassumestheatmosphereisISOTHERMAL;atthesametemperaturethroughout.Infact,asweascendintheatmosphere,temperaturedropsattheLAPSERATEof6.5oCper1000muntilwereachthecoldestpartoftheatmosphere–thetropopause(boundarybetweentroposphereandstratosphere).Abovethisaltitude,intheSTRATOSPHERE,temperatureincreaseswithaltitudeduetoincidentuVabsorptionandre-emissionatlongerwavelengthscausingatmosphericheating.

P = pressure at altitude h metres P0 = sea level pressure m = mean mass of a particle in the atmosphere

( )kTmgh0 ePP /−=

Radioactivity t0 eNN λ−=

Capacitance ( )CRt0 eVV /−=

4

Venus–Earth’s“eviltwin”Venus,namedaftertheRomangoddessoflove,probablywinstheprizefortheastronomicalobjectthatfailstoliveuptoitslabel!ItisprobablytheclosestapproximationtoHellthatwecouldenvisageanywhereintheSolarSystem.Withsurfacetemperaturesoftheorderof480C(andlittlevariationindayandnight)andasurfacepressureof90+Earthatmospheres(equivalenttonearly1000Newtonsoneverysquarecentimetre)eventhemostrobustplanetarylandershaveonlysurvivedtoreturndataforamatterofminutesor,atbest,afewhours.StepoutonVenus’ssurfacewithoutatungstenarmouredhard-shellpressuresuitandyou’dbecrushedandbakedwithinseconds!

Figure03Ourimagesofthesurfacedatebacktothe1970sand1980s.TheSovietVeneraseriesoflanderssurvivedtoreturnsurfacedata,withVeneras9,10,13and14eachreturningonepanoramicfish-eyeviewbeforesuccumbingtotheharshenvironment:

This cross-sectional pressure and temperature profile through the Venusian atmosphere highlights the exponential pressure increase with depth in the atmosphere 1 bar = 100 000N/m2

1 standard Earth atm = 1013.25mb

5

Figure04

ThisVenera13rawimage(1982)attophasbeenenhancedtobringoutfurtherdetails:


TheatmosphereofMars

OnMars,theatmospherehaslessthan1%ofthesea-levelpressureonEarth.Martian

pressuresaregivenwithreferencetoaMartianimaginarysea-levelcalledthemeandatum

becauseMarshasnooceansatpresent!

Mars’atmosphereissoinsubstantialcomparedtoEarth’sthateveninMartiansummer

whereoccasionallythesurfacetemperatureinafewlow-lyinglocalesmightreach20o

C,the

lapserateintheimmediatevicinityofthesurfaceismuchlargerthanonEarth.TheMartian

atmosphere’sheatretentioncapacityissolowthateventwoorthreemetresaboveour

surfaceinmidsummer,itwouldbebelow0o

C.

MisunderstandingsaboutpressuredifferentialsandthehumanbodyThehumanbody,ifexposedtotheMartianorvacuumenvironmentunprotected,would

NOTexplode!Invacuumchamberaccidents,humanshavesurvivedexposuretovacuumof

uptooneminutewithouttheexplosionoftheinternalorgansorskinoreyeballs.The

humanskinisstrongerthanexpectedandwouldfunctiontosomedegreeasapressuresuit

forashortperiodoftime.Bloodwouldnotboilthroughtheskinbutdissolvedgasesinthe

6

bloodstreamwouldstartcascadingoutofsolution–resultinginlethalebullisminashortperiodoftime.

• Explosiveoutgassingofairfromthelungsatoverpressurescorrespondingto10N/cm2(normalatmosphericpressure)wouldbeenoughtoblastoutweakerhumanfrontteeth

• Alotofmisconceptionsconfusedivingdecompressionaccidentswithspacesuit

failures.Intheearly1980sadecompressionaccident(theByfordDolphinincident)resultedinanumberofdiversbeingexplosivelydecompressedfromapressureof9atm(900000Pa)to1atminlessthanasecond.Thisresultedintheexplosivedisintegrationofoneofthediver’sbodies.However,aspacesuitdecompressionwouldresultinapressuregradientfarlesssteepandhencethehumnanbodywouldmostlikelyretainintegrity.

• In1966JohnsonSpaceCenterengineerJamesLeBlancwastestingaspacesuitina

vacuumchamberwhenhissuitdecompressedatanequivalentaltitudeof250000ft(toallintentsandpurposesavacuum).Hislastmemorywasofthesalivaboilingoffhistongueashelostconsciousness.Thechamberwasfloodedwithairwithin14secondsandLeBlancmadeafullrecoverywithindays.

LandingonMars…….ischallenging,tosaytheleast!Thereisenoughofanatmospheretocauseram-airheatingonatmosphericentry,butnotenoughtobeabletorelyontheterminalvelocityofaerodynamicdecelerators(i.e.parachutes)deliveringthespacecraftsafelytothesurface.ThesuccessrateforMartianlandingmissionsisstillonlyjustover50%-afternearlyfourdecadesoflandingattempts,notablefailureshaveincluded:

• Mars2(1971)CrashedonMars(SovietUnion)• Mars3(1971)15secondsofdataandpartialimage(SU)• Mars6(1973)Transmissionsceasedjustbeforelanding(SU)• MarsPolarLander(1999)Enginecutoffwhilst40mabovesurface(US)• DeepSpace2(1999)Unknown(US)• Beagle2(2003)Unknown(UK2003)

SuccesseshaveincludedtheVikinglandersofthe1970s,PathfinderandtheSojournermini-rover(1997)andthespectacularUSMarsExplorationRovers(MER)–SpiritandOpportunity.Launchedin2003withanoperationalexpectancyof90Martiandays(sols),Opportunityhasnowbeenreturningdataforeightyears(Spiritfinallystoppedtransmittingin2010)andbothrovershavetransformedourunderstandingoftheMartianenvironmentandgivenustantalisingcluesastotheplanet’spasthistory.

7

MostrecentlyPhoenix(US)successfullylandedintheMartianArcticin2008andCuriosity(NASA’sMarsScienceLaboratory)iscurrentlyexploringGalecrater,havingsuccessfullylandedinthesummerof2012.Marscurrentlyhoststhreeactivespaceprobesinorbit(MarsOdyssey(NASA),MarsExpress(ESA)andtheMarsReconnaissanceOrbiter(NASA)).


Theaboveimageshowsatrue-colourpanoramaoftheEndurancecraterasexploredbyMER-B(Opportunity)SurfacepressuredatafromNASA’sPathfindermission(1997)Forreference,Earth’smeanpressureis1013.25mb.

Figure07MarsGlobalSurveyor’sthermalemissionspectrometerobtainedthefollowingdataaboutsurfacetemperaturesinthesouthernhemispherefromMartianorbit:

8

Figure08The“frost”inthis1978Viking2imageisnotwatericebutrathersolidCO2thathassublimedoutoftheMartianatmosphereaswinterdrawscloser.

Figure09

FromorbitalandgroundmeasurementswecancombinedatasetstogivethefollowingoverallapproximatepictureoftheMartiansurfaceenvironment:

• Temp(Mean):-46C

• Temp(Max):-5to+20C(verytransient)

• Temp(Min):-90C

• Meansurfacepressure

=8mb

• (Earth=1013.25mb=101325Pa)

• Composition:96%CO2

Theblueskyisafalse-colourartefactfromimageprocessing.

9

ImageReferences:Figure01-ImagefromWeAreAliens!teachingresourcevideo(2012)©NSCCreative2012Figure02-(2012)©NSCCreative2012Figure03-DAILYKOS.COM(2011)GettingtoknowyourSolarSystem(3):Venus[WWW]Availablefrom:http://www.dailykos.com/story/2011/08/28/1008141/-Getting-to-Know-Your-Solar-System-3-Venus[06/12/2012]Figure04-UOREGON.EDU(dateunknown)Venera[WWW]Availablefrom:http://abyss.uoregon.edu/~js/space/lectures/lec11.html[06/12/2012]Figure05-MAHALO.COM(2010)WhatimagesdidRussianVenera13takeofVenus?How

wasVenera13abletosurviveforover30minutesonthesurfaceofVenus?[WWW]Availablefrom:http://www.mahalo.com/answers/what-images-did-russian-venera-13-take-of-venus-how-was-venera-13-able-to-survive-for-over-30-minutes-on-the-surface-of-venus[06/12/2012]Figure06-NASA(dateunknown)MarsRover“Opportunity”Images[WWW]EnduranceCratorAvailablefrom:http://nssdc.gsfc.nasa.gov/planetary/mars/mars_exploration_rovers/merb_images.html[06/12/2012]Figure07-NASA(dateunknown)MarsPathfinderMETSurfaceCalibratedData;Dataset

Description[WWW]Availablefrom:http://starbase.jpl.nasa.gov/mpfl-m-asimet-4-ddr-edl-v1.0/mpam_0001/document/srfrdrds.htm#DataSetOverview[06/12/2012]Figure08-REDORBIT(2003)MGSThermalEmissionSpectrometerImage[WWW]Availablefrom:http://www.redorbit.com/images/pic/3436/mgs-thermal-emission-spectrometer-image/[07/12/2012]Figure09-WIKIPEDIA(2012)MarsViking21i093[WWW]Availablefrom:http://en.wikipedia.org/wiki/File:Mars_Viking_21i093.png[07/12/2012]

1

WeAreAliens!–Classroomactivity4(Physics)UsingTVsandmagnetstoexplainwhyMarsistheschizophrenicworldoftheSolarSystem!Weoftenthinkofspaceasavacuum–buttheSuniscontinuallyemittingastreamofchargedparticles–thesolarwind–inalldirections.Thistorrentofhigh-energyelectronsandprotonshasthecapability,overmillionsofyears,tostripawayaplanetaryatmosphere.Thereasonitdoesn’t,inthecaseofEarth,isbecauseofourglobalplanetarymagneticfield.(CRTTVandmagnetdemo)

Figure01IfweheatapermanentironmagnettoaboveitsCURIEtemperature(about1000K)thenthermalagitationmeansthatindividualatomicdipolemomentsarerandomlyaligned–i.e.thematerialwillloseitspermanentmagneticmoment.TheinterioroftheEarthiswellabovethistemperature–therecan’tbeasolidironmagnetburiedtherethatcreatestheEarth’smagneticfield!CurrentmodellingsuggeststhatliquidcurrentsintheEarth’soutercoregenerateaplanetarymagneticfield–amechanismcalledthegeomagneticdynamo.

Figure02

2

Figure03TheinteractionbetweentheEarth’smagneticfieldandthechargedparticlesofthesolarwind(trillionsofelectriccurrents,ineffect–eachthuscreatingtheirownmagneticfield)causestheparticlestobedeflectedawayfromstrippingawaytheatmosphere.Somegetfunnelledtothepolarregions,causingtheupperatmosphericauroraewhilstothersgettrappedintheEarth’smagneticfieldoscillatingbackandforthinthefamedVanAllenradiationbelts.Figure04–Shownbelow

CurrentlyMarshasnoglobalmagneticfieldofcomparablestrengthtoEarth’s.

3

Figure05–ShownaboveHowever,weseegeologicalevidencefora“fossil”fieldinthepastfromMGS(MarsGlobalSurveyor)data:

Figure06–ShownaboveAsasmallerplanetthanEarth,Marshasalargersurfaceareatovolumeratioandsolostinternalheatquicker.Italsohadlessgravitationalself-accretionenergytostartwithandalowerinventoryofradioactivematerialsinitscorewhichprovidesextra“internalheating”.PerhapsMars’corewasoncewarmenoughtoenabletheliquidmotionnecessarywithinthecoretocreateaplanetarymagneticfield.Asideeffectofthisincreasedcoreheatwouldhavebeenpartialsurfacetectonicactivity–asevidencedbytheenormousshieldvolcanoOlympusMonsandthegianttectoniccrackofVallisMarineris.ItisasifthetectonicengineonMarswasstutteringbutneverbecamegloballyoperational.

Forreference,Earth’smagneticfieldstrengthatthesurface(awayfromthegeomagneticpoles)isapproximately5*10-4Tesla.

ThefiguresforMarsare4to5ordersofmagnitudesmaller.

4

Figure07–ShownaboveAstimewentonandtheplanet’sinteriorcooled,tectonismdiedawayandtheliquidcurrentsnecessaryinthecoretoproduceapowerfulglobalmagneticfieldceasedasthecorecooledandsolidified.Itisalsopossiblethatasequenceofgiantasteroidimpactsdestroyedtheplanetarymagneticfield.Whichevermechanismwasresponsible,theendresultwasthesame:thetenuoussolarwindwasnowabletostartdirectlyinteractingwithMars’atmosphere,strippingitawayinarelentlessprocessoverbillionsofyearswiththefinalresultbeingthebarren,dead(?)worldweobservetoday.

Figure08Couldthisbethefateofourplanet?It’scertainlyapossibilitybutcurrentestimatesgiveusatleast1.5billionyearsbeforetheeffectswouldbesodramaticonourhomeworld.Nevertheless,thishighlightsoneofthebenefitsofplanetaryexploration–unlockingthesecretsofotherworldsgivesusbetterinsightsintoourown.

HereweseethatwiththelackoftectonicplatemovementoftheMartiancrust,themagmaticplumeresponsibleforthecreationoftheOlympusMonssupervolcanocreatedamassive,550kmwidepeakreachingover20kmabovemeandatum.

ThelargestvolcanoesonEarth–theHawaiianislandchain,formedanarcduetorelativemotionoftheoceanicplateoverthemantleplume.

ObservationshaveshownthatMartianauroraarenotconfinedtoregionscoincidentwithplanetarygeomagneticpolesbutareevidentatalllatitudes.

5

Imagereferences:Figure01-AEROSPACEWEB(2012)WateronMars[WWW]Earth'smagneticfielddeflectingthesolarwindAvailablefrom:http://www.aerospaceweb.org/question/astronomy/q0230.shtml[07/12/2012]

Figure02-DISCOVERYENTERPRISE(2012)DowntotheEarth’sCore[WWW]Availablefrom:http://www.discovery-enterprise.com/2012/10/down-to-earths-core.html[07/12/2012]

Figure03-NATIONALATLAS(dateunknown)TheEarthasDynamo[WWW]Availablefrom:http://www.nationalatlas.gov/articles/geology/a_geomag.html[07/12/2012]

Figure04-ASTRO.UMD.EDU(dateunknown)EducationandOutreach;RadiationBeltstheBigPicture[WWW]Availablefrom:http://spp.astro.umd.edu/SpaceWebProj/education.htm[07/12/2012]

Figure05-UNIVERSETODAY(2008)MarsmagneticField[WWW]Availablefrom:http://www.universetoday.com/14949/mars-magnetic-field/[07/12/2012]

Figure06-COLORADO.EDU(dateunknown)MarsmagneticField;MartianVectorMagneticFieldat400km[WWW]Availablefrom:http://lasp.colorado.edu/~bagenal/3750/ClassNotes/Class19/Class19.html[07/12/2012]

Figure07-MPS.MPG.DE(2006)MantleDynamics[WWW]Availablefrom:http://www.mps.mpg.de/projects/planetary-dynamics/mantle.html[07/12/2012]

Figure08-NASA(2011)HowVitalIsaPlanet'sMagneticField?NewDebateRises[WWW]Artist'sconcept:DisappearanceoftheancientmagneticfieldmayhavetriggeredthelossoftheMartianatmosphere.CREDIT:NASAAvailablefrom:http://www.space.com/11187-earth-magnetic-field-solar-wind.html[07/12/2012]

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