NSCI 314

LIFE IN THE COSMOS

10 - SEARCHING FOR LIFE IN OUR SOLAR SYSTEM:

MARS AND THE OUTER PLANETSDr. Karen KolehmainenDepartment of Physics

CSUSB

http://physics.csusb.edu/~karen/

MARS DIAMETER: 53% EARTH MASS: 11% EARTH DENSITY: 3.9 gm/cm³

SUNLIGHT: 43% OF EARTH TEMP: 180 TO 280 K (-90 TO 7oC OR –135 TO 45oF)

ATMOSPHERE: 95% CO2, 3% N2, 2% Ar, H2O & CO2 CLOUDS, <1% OF EARTH PRESSURE

WATER: POLAR ICE CAPS, SUB-SURFACE PERMAFROST(?), NO LIQUID WATER ON SURFACE NOW BUT IT WAS THERE LONG AGO

SURFACE: ROCKY, CRATERED, FORMER (BUT MAYBE NOT CURRENT?) GEOLOGICAL ACTIVITY

January 1997

October 1996 March 1997

EVIDENCE FOR WATER ON MARS IN THE DISTANT PAST (SEVERAL BILLION

YEARS AGO):– DRY RIVER CHANNELS– ERODED FEATURES– CERTAIN TYPES OF ROCKS THAT COULD ONLY HAVE

FORMED IN THE PRESENCE OF WATER– SALTY OCEAN?

MORE RECENTLY (WITHIN THE LAST FEW MILLION YEARS?)– SOME DRAINAGE FEATURES LOOK YOUNG AND

UNERODED.– PERHAPS THERE IS STILL SUB-SURFACE WATER,

AND OCCASIONALLY A LANDSLIDE ON THE SIDE OF A CLIFF (OR SOME SIMILAR EVENT) FREES SOME WATER TO RUN OUT BRIEFLY ONTO THE SURFACE.

180

120

60

0300

240

240

300

120

180

60

0

60°

30°

0°

-30°

-60°

180° 240° 300° 0° 60° 120° 180°

8

4

0

-4

-8

CHALLENGES THAT LIFE ON MARS WOULD FACE VERY LOW ATMOSPHERIC PRESSURE

NO LIQUID WATER ON SURFACE (ATMOSPHERE IS TOO THIN – WATER WOULD BOIL)

COLD

LARGE DAILY TEMPERATURE VARIATION

ULTRAVIOLET BOMBARDMENT OF SURFACE (NO OZONE LAYER)

MARS VIKING LANDER EXPERIMENTS: TESTS FOR LIFE

CARBON ASSIMILATION: MARTIAN SOIL WAS SCOOPED UP AND EXPOSED TO RADIOACTIVELY LABELED (WITH 14C) CO2 AND CO GAS. THEN THE SOIL WAS ANALYZED TO LOOK FOR 14C.

IF THERE WERE MARTIAN ORGANISMS THAT ABSORB CO2 OR CO LIVING IN THE SOIL, THE 14C COULD HAVE GOTTEN INTO THE SOIL VIA METABOLIC PROCESSES IN THE MARTIAN ORGANISMS.

• RESULTS: FOUND 14C IN SOIL, BUT…• HEAT-STERILIZED SOIL GAVE SAME RESULTS. • CAN BE EXPLAINED NON-BIOLOGICAL CHEMICAL

REACTIONS.

MARS VIKING LANDER EXPERIMENTS: TESTS FOR LIFE

LABELED RELEASE: RADIOACTIVELY LABELED (WITH 14C) NUTRIENTS WERE DRIPPED ONTO SCOOPED-UP MARTIAN SOIL. THEN THE GAS ABOVE THE SOIL WAS EXAMINED FOR THE PRESENCE OF 14C.

IF THERE WERE MARTIAN ORGANISMS LIVING IN THE SOIL, THEY MIGHT HAVE ABSORBED THE NUTRIENTS AND THEN RELEASED GASES CONTAINING THE 14C.

• RESULTS: FOUND 14C LABELED GAS, BUT…

• CAN BE EXPLAINED BY INTERACTION OF BROTH AND PEROXIDES (NON-ORGANIC CHEMICALS) IN SOIL, PRODUCING CO2

MARS VIKING LANDER EXPERIMENTS: TESTS FOR LIFE

GAS EXCHANGE: MARTIAN SOIL WAS SCOOPED UP AND ADDED TO A NUTRIENT BROTH. THEN THE GAS ABOVE THE SOIL WAS ANALYZED FOR THE PRESENCE OF O2, CO2, N2, H2, OR CH4

IF THE SOIL CONTAINED MARTIAN ORGANISMS, THEIR METABOLIC PROCESSES MAY HAVE RELEASED ONE OR MORE OF THESE GASES.– RESULTS: O2 PRODUCED, BUT… – ALSO PRODUCED WHEN DONE IN DARKNESS– ALSO PRODUCED WHEN SOIL WAS HEAT-STERILIZED– ALSO PRODUCED WHEN WATER REPLACED BROTH – CAN RESULT FROM CHEMICAL (NOT BIOLOGICAL)

INTERACTION WITH WATER IN BROTH

VIKING LANDER EXPERIMENTS: TESTS FOR LIFE

GAS CHROMATOGRAPH - MASS SPECTROMETER MEASUREMENTS: SCOOPED-UP MARTIAN SOIL WAS BAKED UNTIL VOLATILES (EASILY VAPORIZED MATERIALS) OUTGAS. THE RESULTING GAS WAS ANALYZED, LOOKING FOR ORGANIC MOLECULES.

RESULTS: NONE FOUND

BOTTOM LINE RESULTS OF ALL EXPERIMENTS: RESULTS TANTALIZING, BUT INCONCLUSIVE

MARTIAN METEORITE ALH84001 ONE OF 19 KNOWN METEORITES OF MARTIAN

ORIGIN MARTIAN ORIGIN DETERMINED BY

– COMPOSITION: VOLCANIC ROCK– ISOTOPIC ABUNDANCES– TRAPPED BUBBLES OF GAS CONSISTENT WITH

KNOWN COMPOSITION OF MARTIAN ATMOSPHERE HOW DID IT GET HERE?

– BLASTED OFF MARS IN AN IMPACT 16 MILLION YEARS AGO

– ORBITED THE SUN FOR NEARLY 16 MILLION YEARS– COLLIDED WITH EARTH 13,000 YEARS AGO– FOUND IN ANTARCTICA IN 1984

CONTENTS OF ALH84001 CARBONATE GLOBULES

– INDICATE PAST PRESENCE OF LIQUID WATER– HAVE A LAYERED STRUCTURE THAT LIVING

ORGANISMS CAN PRODUCE– BUT THERE ARE NON-BIOLOGICAL WAYS OF

PRODUCING THIS LAYERING AS WELL

MAGNETITE CRYSTALS – SIMILAR TO THOSE PRODUCED BY SOME

TERRESTRIAL BACTERIA– BUT MAY HAVE A NON-BIOLOGICAL ORIGIN

CONTENTS OF ALH84001 POLYCYCLIC AROMATIC HYDROCARBONS

(PAHs) – ORGANIC MATERIALS USUALLY PRODUCED BY

DECAY OF ORGANISMS ON EARTH– BUT COULD BE PRODUCED IN NON-BIOLOGICAL

WAYS, OR BE A RESULT OF CONTAMINATION AFTER LANDING IN ANTARCTICA

TINY (100 NM) ROD-SHAPED STRUCTURES– RESEMBLE FOSSIL ANAEROBIC EARTH BACTERIA– BUT MUCH SMALLER – PROBABLY TOO SMALL TO BE REAL FOSSILS– COULD BE NON-BIOLOGICAL STRUCTURES OF THE

SAME SHAPE SOME TERRESTRIAL BACTERIA

– PROOF OF CONTAMINATION

PROSPECTS FOR LIFE ON MARS

NO KNOWN EARTH LIFE FORM (NOT EVEN EXTREMOPHILES) COULD SURVIVE ON THE SURFACE OF MARS.

SOME TERRESTRIAL EXTREMOPHILES MIGHT BE ABLE TO SURVIVE UNDERGROUND ON MARS.

IT’S DIFFICULT TO IMAGINE HOW LIFE COULD ARISE UNDER CURRENT MARTIAN CONDITIONS.

BUT 3.5 BILLION YEARS AGO, THERE WAS A THICKER ATMOSPHERE AND LIQUID WATER.

COULD LIFE HAVE EVOLVED ON MARS THEN? IF SO, MARS MAY HAVE SEEDED EARTH WITH

LIFE ???

PROSPECTS FOR LIFE ON MARS COULD LIFE HAVE EVOLVED 3.5 BILLION

YEARS AGO (OR EARLIER), AND SINCE EVOLVED TO ADAPT TO HARSH CONDITIONS?

IF SO, IT MAY STILL SURVIVE– UNDERGROUND (WATER, UV PROTECTION)– AT THE EDGE OF POLAR CAPS

WE NEED TO GO THERE AND CHECK!

SUMMARY THERE IS DEFINITELY NO COMPLEX LIFE ON

MARS. SIMPLE LIFE MAY HAVE EVOLVED LONG AGO ON

MARS, AND THEN IT EITHER BECAME EXTINCT OR ADAPTED TO SURVIVE UNDERGROUND AND/OR IN SPECIALIZED LOCATIONS.

WHAT WENT WRONG?– MARS IS TOO SMALL, GRAVITY IS TOO WEAK,

COULDN’T HOLD ONTO MUCH OF AN ATMOSPHERE.

– ATMOSPHERIC LOSS HELPED BY IMPACTS AND/OR SOLAR WIND.

– ONCE ATMOSPHERE WAS MOSTLY LOST, LIQUID WATER COULDN’T EXIST ON SURFACE.

JUPITER

DIAMETER: 11 X EARTHMASS: 318 X EARTH = MORE THAN REST OF SOLAR SYSTEM (EXCLUDING THE SUN) COMBINEDDENSITY: 1.3 gm/cm³

SUNLIGHT: 4% OF EARTHTEMP: 125 K (–150oC OR –235oF) AT CLOUD TOPS, BUT WARMER DEEP IN ATMOSPHERE

ATMOSPHERE: 86% H, 14% He, TRACES of CH4, NH3,H2O, HIGH WINDS & STORMS

SURFACE: NONE VISIBLE, (ONLY ATMOSPHERE IS VISIBLE), THERE IS PROBABLY A SMALL ROCKY CORE AND A LIQUID HYDROGEN INTERIOR

SATURN DIAMETER: 9.5 X EARTH MASS: 95 X EARTH DENSITY: 0.7 gm/cm³

SUNLIGHT: 1% OF EARTH TEMP: 90 K (-185 oC or –300 oF) AT CLOUD TOPS,

WARMER DEEPER DOWN

ATMOSPHERE: 86% H, 14% He, TRACES of CH4, NH3, H2O, HIGH WINDS & STORMS

SURFACE: NONE VISIBLE, PROBABLY SMALL ROCKY CORE AND LIQUID HYDROGEN INTERIOR

RINGS: LARGEST RING SYSTEM OF ANY PLANET, COMPOSED MOSTLY OF CHUNKS OF WATER ICE

URANUS & NEPTUNE DIAMETER: 4.0, 3.9 X EARTH MASS: 15, 17 X EARTH DENSITY: 1.2, 1.7 gm/cm³

SUNLIGHT: 0.3%, 0.1% OF EARTH TEMP: 64 K (-210 oC OR –345 oF) FOR URANUS, 50

K(-220 oC OR –370 oF) FOR NEPTUNE AT CLOUD TOPS, WARMER DEEPER DOWN

ATMOSPHERE: 84% H, 14% He, 2-3% CH4 (NH3 & H2O FROZEN), BLUE COLORS DUE TO METHANE

SURFACE: NONE VISIBLE, PROBABLY ROCKY CORES AND LIQUID HYDROGEN INTERIOR

LIFE ON THE OUTER PLANETS? DEEP ENOUGH DOWN IN THE ATMOSPHERE, IT

IS WARM ENOUGH FOR LIQUID WATER DROPS. SIMPLE ORGANIC MOLECULES HAVE BEEN

FOUND IN THE ATMOSPHERES. SUGGESTION: PERHAPS BLIMP-LIKE LIFE

FORMS COULD FLOAT OR FLY IN THE ATMOSPHERE.

IF THESE EXIST, JUPITER IS THE MOST LIKELY SITE. IT IS THE WARMEST OF THE OUTER PLANETS, AND THEREFORE HAS THE MOST ACTIVE CHEMISTRY.

PROBLEM: STRONG CIRCULATION PATTERNS IN THE ATMOSPHERE MIGHT PREVENT COMPLEX ORGANIC MOLECULES FROM FORMING, SO HOW COULD LIFE GET STARTED?

DIAMETER: 20% OF EARTH MASS: 0.2% OF EARTH DENSITY: 2.1 gm/cm³

SUNLIGHT: 0.06% OF EARTH TEMP: 45 K (-230 oC OR –380 oF) ATMOSPHERE: VERY THIN, METHANE (CH4) ICE

CRYSTALS SURFACE: ICE AND ROCK, METHANE (CH4) ICE MOON: CHARON NOTE: PLUTO IS NO LONGER CONSIDERED TO BE

A PLANET. IT IS JUST A LARGE KUIPER BELT OBJECT.

PLUTO

PLUTO AND CHARON PLUTO IS SMALLER THAN ANY PLANET IN THE

SOLAR SYSTEM - ONLY 2/3 SIZE OF EARTH’S MOON

MOON (CHARON) IS HALF THE SIZE OF PLANET (PLUTO)

BOTH ARE ICY/ROCKY BODIES BOTH IN SYNCHRONOUS ROTATION SIZE AND COMPOSITION SIMILAR TO MOONS

OF OUTER PLANETS OR LARGEST KUIPER BELT OBJECTS (COMETS)

WAY TOO COLD FOR LIFE (NO WARMER AREAS LIKE GAS GIANT PLANETS DEEP DOWN IN ATMOSPHERE)

NO OFFICIAL NAME YET UNOFFICIALLY CALLED XENA BY SOME, BUT THIS IS

UNLIKELY TO BE THE OFFICIAL NAME DIAMETER: 20 TO 25% OF EARTH (A LITTLE LARGER

THAN PLUTO) MASS: PROBABLY 0.2 TO 0.3% OF EARTH DENSITY: PROBABLY ABOUT 2 gm/cm³ SUNLIGHT: 0.01% OF EARTH TEMPERATURE: ABOUT 3O K (-245 oC OR –405 oF) ATMOSPHERE: ?? (NOT MASSIVE ENOUGH TO HOLD

ONTO MUCH OF ONE) SURFACE: ICE AND SOME ROCK, METHANE (CH4) ICE MOON: HAS ONE (NOT NAMED YET EITHER)

NEW LARGE KUIPER BELT OBJECT

THIS OBJECT AND PLUTO ARE SIMILAR. BOTH ARE:•SMALLER THAN ALL 8 PLANETS (MERCURY THROUGH NEPTUNE)•MOSTLY ICE, A LITTLE ROCK•ORBITS AREN'T AS CIRCULAR AS THOSE OF THE 8 PLANETS•ORBITS ARE TIPPED SLIGHTLY RELATIVE TO THE DISK FORMED BY THE PLANE OF THE 8 PLANETS

SEEM MORE LIKE BIG KUIPER BELT OBJECTS •RECALL THAT THE KUIPER BELT IS THE INNER GROUP OF COMETS IN OUR SOLAR SYSTEM. (THE OORT CLOUD IS THE OTHER GROUP OF COMETS FARTHER FROM THE SUN.)

NEW LARGE KUIPER BELT OBJECT

THE DISCOVERY OF THIS OBJECT PROMPTED RECONSIDERATION OF THE DEFINITION OF A PLANET. •THERE MAY BE MANY LARGE KUIPER BELT OBJECTS THIS LARGE WAITING TO BE DISCOVERED. •DO WE WANT TO CALL THEM ALL PLANETS?•IF NOT, THEN TO BE CONSISTENT, PLUTO SHOULDN'T BE CALLED A PLANET EITHER.

OFFICIAL DECISION (RECENT): NEITHER PLUTO NOR THIS OBJECT ARE PLANETS. INSTEAD, THEY ARE LARGE KUIPER BELT OBJECTS (COMETS).

THE RULES ASTRONOMERS HAVE ESTABLISHED FOR NAMING PLANETS ARE DIFFERENT THAN FOR NAMING OTHER OBJECTS, SO NO DECISION ON THE NAME OF THE RECENTLY DISCOVERED OBJECT WAS MADE BEFORE THE DEFINITION OF A PLANET WAS DECIDED UPON.

NEW LARGE KUIPER BELT OBJECT