NSCI 314 LIFE IN THE COSMOS 9 - SEARCHING FOR LIFE IN OUR SOLAR SYSTEM: MARS Dr. Karen Kolehmainen Department of Physics CSUSB

MARS DIAMETER: 53% EARTH MASS: 11% EARTH DENSITY: 3.9 gm/cm³ SUNLIGHT: 43% OF EARTH TEMP: 140 TO 280 K (-130 TO 7 o C OR –200 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 CURRENTLY, BUT LARGE AMOUNTS (?) OF LIQUID WATER ON SURFACE WHEN PLANET WAS YOUNG SURFACE: ROCKY, CRATERED, FORMER (BUT MAYBE NOT CURRENT?) GEOLOGICAL ACTIVITY

January 1997 October 1996March 1997

SEASONS ON MARS SEASONS SIMILAR TO EARTH –MARS' AXIS IS TILTED BY 25 O, ALMOST THE SAME DEGREE OF TILT AS THE EARTH'S AXIS –EACH SEASON LASTS TWICE AS LONG, SINCE THE YEAR IS TWICE AS LONG HOWEVER, UNLIKE EARTH, MARS' ORBIT IS SUBSTANTIALLY ELLIPTICAL –MARS IS CLOSER TO THE SUN IN NORTHERN HEMISPHERE WINTER, SOUTHERN HEMISPHERE SUMMER –MARS IS FARTHER FROM THE SUN IN NORTHERN HEMISPHERE SUMMER, SOUTHERN HEMISPHERE WINTER –A PLANET MOVES FASTER IN ITS ORBIT WHEN IT IS CLOSER TO THE SUN

SEASONS ON MARS THE RESULT IS: IN THE NORTHERN HEMISPHERE: –WINTER IS WARM AND SHORT –SUMMER IS COOL AND LONG IN THE SOUTHERN HEMISPHERE: –WINTER IS COLD AND LONG –SUMMER IS HOT AND SHORT REMEMBER THAT “WARM” AND “HOT” ARE USED RELATIVELY. MARS IS MUCH COLDER THAN EARTH OVERALL. IN MID-DAY ON A WARM DAY IN THE SUMMER NEAR THE EQUATOR ON MARS, THE TEMPERATURE MIGHT REACH 60 O F

SEASONS ON MARS POLAR CAPS: –WATER ICE ALL YEAR ROUND –FROZEN CO 2 (“DRY ICE”) IN WINTER CAP 1/3 OF THE TOTAL CO 2 IN THE ATMOSPHERE MOVES FROM ONE POLAR CAP TO THE OTHER POLAR CAP AS THE SEASONS CHANGE. THE RESULT IS VERY STRONG WINDS BLOWING FROM THE SUMMER POLAR CAP TO THE WINTER POLAR CAP. WINDS CAUSE HUGE DUST STORMS, WHICH OFTEN OBSCURE SURFACE DETAILS.

EVIDENCE FOR LIQUID WATER ON THE SURFACE OF MARS IN THE DISTANT PAST (2-3 BILLION YEARS AGO): –DRY RIVER CHANNELS –ERODED FEATURES –PRESENCE OF CERTAIN TYPES OF ROCKS THAT COULD HAVE FORMED ONLY IN THE PRESENCE OF WATER –SALTY OCEAN?

EVIDENCE FOR LIQUID WATER ON THE SURFACE OF MARS MORE RECENTLY? –SOME DRAINAGE FEATURES LOOK YOUNG AND UNERODED. IF THEY WERE OLDER, DUST SHOULD HAVE COVERED THEM UP BY NOW. –IN A FEW CASES, PHOTOGRAPHS TAKEN SEVERAL YEARS APART SHOW CHANGES. –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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HISTORY OF WATER ON MARS LONG AGO, WHEN MARS HAD LIQUID WATER, IT MUST HAVE BEEN WARMER AND HAD A THICKER ATMOSPHERE (TO PREVENT WATER FROM BOILING). –ORIGINALLY MARS OUTGASSED ENOUGH CO 2 FROM VOLCANOES TO HAVE 400 x AS MUCH AS IT HAS TODAY. –THIS WOULD HAVE PRODUCED A SIGNIFICANT GREENHOUSE EFFECT, WARMING MARS TO TEMPERATURES HIGH ENOUGH FOR LIQUID WATER.

HISTORY OF WATER ON MARS WHAT HAPPENED TO CHANGE MARS? MOST CO 2 AND H 2 O ESCAPED INTO SPACE –MARS IS SO LIGHT THAT ITS GRAVITY ISN'T STRONG ENOUGH TO HOLD ONTO FAST-MOVING GAS MOLECULES –SOME GAS MAY HAVE BEEN BLASTED AWAY BY IMPACTS –SOME GAS MOLECULES STRIPPED OUT OF ATMOSPHERE BY SOLAR WIND MAGNETIC FIELD WOULD HAVE PROTECTED EARLY MARS FROM SOLAR WIND AS MARS COOLED, CORE SOLIDIFIED AND MAGNETIC FIELD WEAKENED, ALLOWING SOLAR WIND TO GET IN –UV LIGHT FROM SUN DISSOCIATED H 2 O MOLECULES, H ESCAPED TO SPACE, O COMBINED WITH ROCKS (-- > RUST)‏

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 (BROUGHT FROM EARTH). 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 GAS EXCHANGE: MARTIAN SOIL WAS SCOOPED UP AND ADDED TO A NUTRIENT BROTH (BROUGHT FROM EARTH). 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

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

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 INTERESTING, BUT INCONCLUSIVE

METHANE IN MARTIAN ATMOSPHERE? DISCOVERED BY EUROPEAN SPACECRAFT IN 2004 – VERIFICATION STILL NEEDED METHANE CAN BE PRODUCED BY LIFE, VOLCANOES, OR LARGE COMETARY IMPACTS METHANE LASTS ONLY A FEW CENTURIES IN THE ATMOSPHERE –NO RECENT LARGE COMETARY IMPACT –COLD BE VOLCANIC IN ORIGIN, BUT THAT IS STILL EXCITING CURRENT GEOLOGICAL ACTIVITY WOULD IMPLY POCKETS OF WARMTH BELOW THE SURFACE

MARTIAN METEORITE ALH84001 ONE OF 30 OR 40 KNOWN METEORITES OF MARTIAN ORIGIN MARTIAN ORIGIN DETERMINED BY –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 LAYERING AS WELL MAGNETITE CRYSTALS –SIMILAR TO THOSE PRODUCED BY 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?

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 EDGE OF POLAR CAPS FUTURE SPACECRAFT MISSIONS WILL CONTAIN ADDITIONAL EXPERIMENTS TO LOOK FOR LIFE.

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

MOONS OF MARS TWO SMALL MOONS – PHOBOS AND DEIMOS SUCH LOW MASS THAT GRAVITY ISN'T STRONG ENOUGH TO PULL THEM INTO SPHERICAL SHAPE PROBABLY CAPTURED ASTEROIDS –RECALL THAT MOST ASTEROIDS ARE FOUND BETWEEN THE ORBITS OF MARS AND JUPITER. THUS, MANY ASTEROIDS COME CLOSE TO MARS, AND MARS' GRAVITY COULD CAPTURE THEM.