2nd brazilian corot workshop - ubatuba, nov 6 2005 why being earth-centered when searching for life...

2nd Brazilian COROT Workshop - Ubatuba, Nov 6 2005

WHY BEING EARTH-CENTERED WHEN SEARCHING FOR LIFE IN THE COSMIC NEIGHBORHOOD?

1Divisão de Astrofísica, - INPE2Instituto de Biofísica Carlos Chagas Filho - UFRJ3Instituto Astronômico e Geofísico - IAG/USP4Instituto de Química - UFRJ5Observatório do Valongo - UFRJ

Carlos Alexandre Wuensche1

Claudia Lage2

Amâncio Friaça3

Sérgio Pilling4

Heloísa Boechat-Roberty5

Contato: [email protected]


A cosmological perspective to

search of life in the Universe...

Life building blocks come

from these components...

Ωb = 0.04 ΩT

LET´S GIVE IT UP, THEN...

Bennett et al., ApJ Suppl Series 2003

NOT!


How can we define life?

• It is quite a subjective concept, but we can list some common characteristics (J. Schneider, astro-ph/9604131, 1996; Szostak et al., Nature, 2001, Bains,

Astrobiology 2005)– Complex and diversified interactions with the

environment– System out of thermodynamical equilibrium– Memory + reading/recovering mechanism– Self-replication capability

Life is a self-sustained chemical system, capable of evolution in a Darwinian sense (Joyce 1994).


For a practical search, restrictive hipothesis...

• What kind of complex systems?– Liquid crystals, plasmas...

• Conservative hipothesis – a chemical system.– C, Si?

• Presence of a liquid millieu?– H2O: excelent solvant and abundant in the Universe

• Existence of a solid/liquid interface?– Favours molecular interactions...

Questions

1) Does life need, necessarily, such atoms and physical-chemical conditions?

2) Can life develop, in another planet, under totally different conditions?


Most definitions tend to be EMost definitions tend to be EARTH-ARTH-CENTEREDCENTERED

So, let´s understand “Earth model”So, let´s understand “Earth model”


HABITABLE ZONE (68% e 95%)

Lineweaver et al., Science, 303, 59 (2004)


•[X/H]=log(X/H)-log(X/H)Sun.

•Components: halo, thick and

thin disks.•Universe age: 13 Gyr. •Solar age: 4.6 Gyr

Minimum abundance to form terrestrial

planets: [X/H]=-1.0 +/- 0.3.

(Lineweaver, Icarus, 151, 307, 2001)

Biologically interesting elements abundance in the Galaxy


Stellar habitable zone

R

Main assumptions: Surface H2O for ~ Gyear, geological activity, CO2-H2O-N2 atmosphere, B-field, climate stability, resistance to catastrophes for ~ Gyear


In the early Earth:

Miller & Urey, 1961


Saladino et al., Chem. Biochem, 2004

Images´ source: http://www.whfreeman.com/life/update/

Pre-cellular life... Where does it come from?• Nucleic acids required!

• But NO NUCLEIC ACIDS were found in Miller & Urey experiment.

• How could they be formed? Polymerisation of cyanide, which can be readily formed in a primitive atmosphere!

• So what? This still doesn't look much like a nucleic acid! However, the tetramer can be rearranged as follows:


Pathways for biomolecule formation in space:the glycine case - Environment

1 Ori C

ORION M42

TRAPEZIUM - HST 2003

Young starsT ~ 30000K X-rays

Lx ~ 2 x1032 erg s-1 (Chandra)ne ~ 5000 neMI

Excitation of rotational-vibrational levels


Pathways for biomolecule formation in space:the glycine case - Model

Tielens & Hollenbach (1985) ApJ 291, 747

Schulz etal 2001 ApJ, 549, 4441Schulz etal 2001 ApJ, 549, 4441

FUV ~ 10-100 erg cm-2 s-1 ngas ~ 104-105 cm-3 (107-103 cm-3)T ~ 50-200 K (10 - 1000 K)

PDRs Typical Features


Measurements in spaceAcetic acid

Formic acid

NH2CH2COOH

++(-H(-H22O)O)

methanolamine

++

Methylenimine

Ammonia

++(-H(-H22))

Formic acid ice/gas ratio ~ Formic acid ice/gas ratio ~ 10000!10000!

Low resistence to radiation field?

Which pathway is more probable?

Formation via ice or gas phase? ++ (-H(-H22O; -H)O; -H)

Protonated

methanolamine

++(-H2O; -H)

Protonated

Hidroxilamine

Ehrenfreund et al 2001 JGR , 106, E12, 33291; Whittet et al 1996 Ehrenfreund et al 2001 JGR , 106, E12, 33291; Whittet et al 1996 A&A 315, L357A&A 315, L357


Results from space

Liu etal 2002 Apj 576, 255

(~2 x 1015 cm2)

Remijan etal 2002 ApJ 576, 264

Kuan etal 2004 ASR, 33, 31

(~6x 1015 cm2)

Through acetic

acid

Through

formic acid


Results from collisions at LNLS


H

C

N

Recent detection of a PANH in the IRHudgins et al. ApJ, 2005

• Spitzer detected PANHs in various galaxies, besides our own. • First direct evidence for the presence of a prebiotic interesting compound in

space.• Presence of N is essential in biologically interesting compounds (clorophyle).• The presence of a planet is no longer necessary for the formation of a PANH.

Caffeine


Porto de Mello et al., Astrobiology, 2005

Astrobiologically interesting stars and planets

Explore the star/planet contrast in the thermal IR(Des Marais et al 2002, Segura et al 2003)

Thermal IRCO2 15 mO3 9.6 mH2O: 6.3 m + 12 m band to microwaves CH4 7.7 mWindow at 8-12 m: surface temperatureColor temperature + flux = radius (problems with clouds)


Any alternatives at this point???

• Other liquids may define other biochemistries

• Ammonia (Jupiter satellites), methane/ethane

(Titan), nitrogen (silicon-oriented)

• Light (mostly IR) on the surface of Titan may

allow photosynthesis-like processes, even at

low temperatures.

• Chemolitotrophy possibly available in any

liquid environment (Galilean satellites).


Water-based oceans

Other liquid

possibilities

OUR SOLAR SYSTEM´S LIQUID POSSIBILITIES

water/ammonia (surface lakes)

water/ammonia (subsurface)

methane/ethane

(surface lakes)

nitrogen (su

rface)

nitrogen (su

bsurface)


Criptoendoliths

Thermophile bacteria

Hidrotermal vents

Hot geisers and volcans

Extremophiles survival chart

Antarctica• Temperature: -15° C < T < 230° C• 0 < pH < 12• 0 < Pressure < 1200 atm• No mandatory oxygen-based metabolism• 20-40 Myears of dormancy• 2 ½ years in space, at 20 K, with no

nutrients, water and exposed to radiation

(Strep. Mitis)


What do we suggest?• Carbon based, DNA-like search, in planetary

systems

– Targeting small constituints of organic compounds – IR/X

(Pilling et al., A&A 2005)

– Targeting PANHs – IR (Hodges et al., ApJ 2005)

• Other alternatives (chemical/physical)

– Other liquids/fluids demand a different chemistry (not

CHON based) due to thermodynamical requirements

(Bains, Astrobiology 2005).

– Self-sustained ability to disturb a local environment

(Bains, Astrobiology 2005).


WHERE IS DNA OR ANY OF ITS RELATIVES?

The end…

… or the beginning?????

2nd brazilian corot workshop - ubatuba, nov 6 2005 why being earth-centered when searching for life...

Documents

life need

life building blocks

precellular life

surface h2o

early earth

nucleic acids

biomolecule formation

physicalchemical conditions