NSCI 314 LIFE IN THE COSMOS 10 - SEARCHING FOR LIFE IN OUR SOLAR SYSTEM: MARS AND THE OUTER PLANETS Dr. Karen Kolehmainen Department of Physics CSUSB

MARS DIAMETER: 53% EARTH MASS: 11% EARTH DENSITY: 3.9 gm/cm³ SUNLIGHT: 43% OF EARTH TEMP: 180 TO 280 K (-90 TO 7 o C OR –135 TO 45 o F) ATMOSPHERE: 95% CO 2, 3% N 2, 2% Ar, H 2 O & CO 2 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 1996March 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.

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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 14 C) CO 2 AND CO GAS. THEN THE SOIL WAS ANALYZED TO LOOK FOR 14 C. IF THERE WERE MARTIAN ORGANISMS THAT ABSORB CO 2 OR CO LIVING IN THE SOIL, THE 14 C COULD HAVE GOTTEN INTO THE SOIL VIA METABOLIC PROCESSES IN THE MARTIAN ORGANISMS. RESULTS: FOUND 14 C 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 14 C) NUTRIENTS WERE DRIPPED ONTO SCOOPED-UP MARTIAN SOIL. THEN THE GAS ABOVE THE SOIL WAS EXAMINED FOR THE PRESENCE OF 14 C. IF THERE WERE MARTIAN ORGANISMS LIVING IN THE SOIL, THEY MIGHT HAVE ABSORBED THE NUTRIENTS AND THEN RELEASED GASES CONTAINING THE 14 C. RESULTS: FOUND 14 C LABELED GAS, BUT… CAN BE EXPLAINED BY INTERACTION OF BROTH AND PEROXIDES (NON-ORGANIC CHEMICALS) IN SOIL, PRODUCING CO 2

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 O 2, CO 2, N 2, H 2, OR CH 4 IF THE SOIL CONTAINED MARTIAN ORGANISMS, THEIR METABOLIC PROCESSES MAY HAVE RELEASED ONE OR MORE OF THESE GASES. –RESULTS: O 2 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 EARTH MASS: 318 X EARTH = MORE THAN REST OF SOLAR SYSTEM (EXCLUDING THE SUN) COMBINED DENSITY: 1.3 gm/cm³ SUNLIGHT: 4% OF EARTH TEMP: 125 K (–150 o C OR –235 o F) AT CLOUD TOPS, BUT WARMER DEEP IN ATMOSPHERE ATMOSPHERE: 86% H, 14% He, TRACES of CH 4, NH 3,H 2 O, 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 o C or –300 o F) AT CLOUD TOPS, WARMER DEEPER DOWN ATMOSPHERE: 86% H, 14% He, TRACES of CH 4, NH 3, H 2 O, 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 o C OR –345 o F) FOR URANUS, 50 K(-220 o C OR –370 o F) FOR NEPTUNE AT CLOUD TOPS, WARMER DEEPER DOWN ATMOSPHERE: 84% H, 14% He, 2-3% CH 4 (NH 3 & H 2 O 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 o C OR –380 o F) ATMOSPHERE: VERY THIN, METHANE (CH 4 ) ICE CRYSTALS SURFACE: ICE AND ROCK, METHANE (CH 4 ) 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 o C OR –405 o F) ATMOSPHERE: ?? (NOT MASSIVE ENOUGH TO HOLD ONTO MUCH OF ONE) SURFACE: ICE AND SOME ROCK, METHANE (CH 4 ) 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