nsci 314 life in the cosmos 11 - searching for life in our solar system: the outer planets and their...
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NSCI 314
LIFE IN THE COSMOS
11 - SEARCHING FOR LIFE IN OUR SOLAR SYSTEM:
THE OUTER PLANETS AND THEIR MOONSDr. Karen KolehmainenDepartment of Physics
CSUSB
http://physics.csusb.edu/~karen/
JUPITERDIAMETER: 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: ONLY ATMOSPHERE IS VISIBLESTRUCTURE: SMALL ROCKY CORE, COVERED BY A LAYER OF METALLIC HYDROGEN, THEN A LAYER OF LIQUID HYDROGEN, THEN THE ATMOSPHERE
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: ONLY ATMOSPHERE IS VISIBLE STRUCTURE: SMALL ROCKY CORE, COVERED BY
LAYERS OF METALLIC HYDROGEN AND LIQUID HYDROGEN, THEN ATMOSPHERE
RINGS: LARGEST RING SYSTEM OF ANY PLANET, COMPOSED MOSTLY OF CHUNKS OF WATER ICE
URANUS DIAMETER: 4 X EARTH MASS: 15 X EARTH DENSITY: 1.2 gm/cm³
SUNLIGHT: 0.3% OF EARTH TEMP: 64 K (-210 oC OR –345 oF) AT CLOUD TOPS,
WARMER DEEPER DOWN
ATMOSPHERE: 84% H, 14% He, 2-3% CH4 (NH3 & H2O FROZEN), BLUE COLORS DUE TO METHANE
SURFACE: ONLY ATMOSPHERE VISIBLE STRUCTURE: SMALL ROCKY CORE, COVERED
BY LAYER OF WATER, METHANE, AND AMMONIA, THEN ATMOSPHERE
NEPTUNE DIAMETER: 3.9 X EARTH MASS: 17 X EARTH DENSITY: 1.7 gm/cm³
SUNLIGHT: 0.1% OF EARTH TEMP: 50 K(-220 oC OR –370 oF) AT CLOUD TOPS,
WARMER DEEPER DOWN
ATMOSPHERE: 84% H, 14% He, 2-3% CH4 (NH3 & H2O FROZEN), BLUE COLORS DUE TO METHANE
SURFACE: ONLY ATMOSPHERE VISIBLE STRUCTURE: SMALL ROCKY CORE, COVERED
BY LAYER OF WATER, METHANE, AND AMMONIA, THEN ATMOSPHERE
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?
MOONS OF OUTER PLANETS MIXTURE OF ICE AND ROCK
LOTS OF THEM
EACH PLANET WITH ITS MOONS RESEMBLES A MINIATURE SOLAR SYSTEM
SMALL MOONS ARE IRREGULARLY SHAPED, WITH NO ATMOSPHERES, NOT GOOD CANDIDATES FOR LIFE
LARGER ONES ARE SPHERICAL, SOME HAVE ATMOSPHERES OR ARE INTERESTING IN OTHER WAYS
CHARACTERISTICS OF LARGE MOONS
Planet NameDensity (g/cm3)
Mass (Moon=1)
Diameter(Moon=1)
Earth
Jupiter
Jupiter
Jupiter
Jupiter
Saturn
Neptune
Moon
Io
Europa
Ganymede
Callisto
Titan
Triton
(Pluto)
3.3
3.5
3.0
1.9
1.9
1.9
2.1
2.1
1
1.2
0.7
2.0
1.5
1.8
0.3
0.17
1
1.1
0.9
1.5
1.4
1.5
0.8
0.65
TIDAL FORCES AND MOONS THE SIDE OF THE MOON CLOSEST TO ITS PLANET
EXPERIENCES A STRONGER GRAVITATIONAL PULL FROM THE PLANET THAN DOES THE SIDE OF THE MOON FARTHEST FROM THE PLANET. THIS PULLED THE MOON INTO AN ELONGATED SHAPE.
AS THE MOON ROTATED ON ITS OWN AXIS, ITS SHAPE KEPT CHANGING TO KEEP THE BULGES ON A LINE FACING THE PLANET. THIS CAUSED FRICTION INSIDE THE MOON, WHICH SLOWED ITS ROTATION.
JUST LIKE WITH THE EARTH’S MOON, THIS HAS LOCKED THE MOON INTO “SYNCHRONOUS ROTATION” WITH THE PLANET. ONE SIDE OF THE MOON ALWAYS FACES TOWARDS THE PLANET, AND THE OTHER SIDE FACES AWAY FROM THE PLANET.
TIDAL FORCES AND MOONS AS THE ORIGINAL ROTATION OF THE MOON WAS
SLOWING (BEFORE IT WAS LOCKED INTO SYNCHRONOUS ROTATION), INTERNAL FRICTION HEATED THE MOON ENOUGH TO MELT IT, LEADING TO A DIFFERENTIATED (LAYERED) STRUCTURE.
TIDAL FORCES ALSO AFFECTED ORBITS OF MOONS AROUND THEIR PLANETS, LOCKING THEM INTO “RESONANCES.”– EXAMPLE: MOON FARTHER OUT ORBITS IN TWICE
THE TIME OF ONE CLOSER IN. ORBITS ARE ELLIPTICAL (NOT CIRCULAR), SO SHAPE
OF MOON VARIES SLIGHTLY THROUGHOUT ITS ORBIT AROUND ITS PLANET.– MORE ELONGATED WHEN CLOSER TO PLANET– MORE SPHERICAL WHEN FARTHER AWAY– THIS LEADS TO CONTINUING INTERNAL FRICTION,
HEATING THE INTERIOR OF THE MOON.
TIDAL EFFECTS ON MOONS AS A RESULT, THE INTERIORS OF THE
LARGE MOONS OF THE OUTER PLANETS ARE WARMER THAN WE WOULD EXPECT BASED ON THEIR DISTANCE FROM THE SUN AND THEIR SIZE. (THEY'RE SMALL, SO THEY LOST HEAT RAPIDLY).
THE LARGER THE MOON AND THE CLOSER IT IS TO ITS PLANET, THE GREATER THE AMOUNT OF TIDAL HEATING.
THIS EFFECT MAKES SOME MOONS WARM ENOUGH TO BE POSSIBLE CANDIDATES FOR LIFE!
MAJOR MOONS OF JUPITER (IN ORDER OUT FROM JUPITER, THEREFORE
HOTTEST TO COLDEST)
IO
EUROPA
GANYMEDE
CALLISTO
IO CLOSEST MOON TO JUPITER, SO TIDAL EFFECTS
ARE LARGEST HIGHEST DENSITY - ROCKIER THAN OTHER
MOONS, TOO HOT INSIDE FOR ICE HOT ENOUGH TO BE COMPLETELY MOLTEN
INSIDE LOTS OF SULFUR ON SURFACE MANY ACTIVE VOLCANOES ERUPTING
CONSTANTLY MORE VOLCANOES THAN ANY OTHER OBJECT IN
THE SOLAR SYSTEM NOT A GOOD PROSPECT FOR LIFE: NO WATER,
LITTLE OR NO ATMOSPHERE, AND LARGE TEMPERATURE EXTREMES
EUROPA NEXT LARGE MOON OUT FROM JUPITER WARM INTERIOR, NOT AS HOT AS IO COMPOSITION:
– ROCKY AND/OR METALLIC CORE – SURROUNDED BY LIQUID WATER OCEAN (?)
50 TO 150 KM DEEP– COVERED BY CRUST OF CRACKED ICE 20
TO 25 KM THICK– NO ATMOSPHERE, BUT ICE CRUST
PREVENTS WATER FROM BOILING INTO SPACE
FEW CRATERS
EVIDENCE FOR OCEAN ON EUROPA FEW IMPACT CRATERS
– IMPACT BREAKS THROUGH ICE, WATER FROM BELOW FILLS IN CRATER AND FREEZES
CHAOTIC TERRAIN– PATCHWORK RIDGED PATTERN OF
ICEBERGS FROZEN IN PLACE STAINS ON CRUST INDICATE UPWELLING OF
WATER CONTAINING DISSOLVED (ORGANIC?) MATERIALS
MAGNETIC FIELD– IMPLIES PRESENCE OF ELECTRICALLY
CONDUCTING LIQUID MATERIAL (SALT WATER)
LIFE ON EUROPA? NO ATMOSPHERE, BUT ICE PREVENTS
WATER FROM BOILING AND PROVIDES UV PROTECTION
ENERGY SOURCE:– HYDROTHERMAL VENTS?– UNDERSEA VOLCANOES?– RADIOACTIVE DECAY IN INTERIOR OF MOON?– PHOTOSYNTHESIS COULD OCCUR IN POCKETS
OF WATER DIRECTLY UNDER THINNER ICE? (BUT NOT MUCH SUNLIGHT)
– HIGH ENERGY ELECTRICALLY CHARGED PARTICLES ARE ACCELERATED BY JUPITER'S MAGNETIC FIELD AND HIT ICE AT HIGH SPEEDS
– UV PHOTONS FROM SUN HIT ICE
LIFE ON EUROPA? PROBABLY NO COMPLEX LIFE, BUT MAYBE
SIMPLE LIFE FORMS– PROBABLY NOT ENOUGH ENERGY TO
SUPPORT LARGE AND COMPLEX ECOSYSTEM
SPACECRAFT MISSION PLANNED, FUNDING CUT– WILL DRILL THROUGH ICE AND RELEASE
SUBMARINE IF WE DO FIND EVEN SIMPLE LIFE ON EUROPA
(OR ANYWHERE ELSE IN OUR SOLAR SYSTEM), IT WILL MAKE US MUCH MORE OPTIMISTIC ABOUT FINDING EXTRATERRESTRIAL LIFE IN GENERAL.
GANYMEDE NEXT LARGE MOON OUT FROM JUPITER LARGEST MOON IN SOLAR SYSTEM (BIGGER
THAN MERCURY) ICE CRUST WITH A MIXTURE OF:
– LIGHTER YOUNGER GROOVED TERRAIN (SIMILAR TO EUROPA), AND
– DARKER OLDER CRATERED TERRAIN MAY BE AN OCEAN UNDER THE ICE, BUT
EVIDENCE IS WEAKER THAN FOR EUROPA– MAGNETIC FIELD– OCCASIONAL FLOODING AND FREEZING
HAS FILLED IN CRATERS IN SOME AREAS COLDER THAN EUROPA, SO ICE IS THICKER
CALLISTO COLDEST OF JUPITER’S MAJOR MOONS SOME EVIDENCE FOR AN OCEAN UNDER THE
ICE– MAGNETIC FIELD– WEAKER EVIDENCE THAN EITHER EUROPA
OR GANYMEDE MORE HEAVILY CRATERED, SO LESS
FLOODING OF SURFACE BY WATER HUGE IMPACT CRATER VALHALLA
– IMPACT MELTED ICE TEMPORARILY– WAVES SPREADING OUT FROM IMPACT
WERE FROZEN IN PLACE– NO BULGE ON OPPOSITE SIDE SUGGESTS
LIQUID INTERIOR PRESENT TO ABSORB SHOCK
MOONS OF SATURN
MOST ARE SMALL BODIES CONSISTING OF A MIXTURE OF ICE AND ROCK, WITH NO ATMOSPHERES.
TITAN IS AN EXCEPTION: A LARGER ICE/ROCK BODY WITH A THICK ATMOSPHERE.
TITAN LARGEST MOON OF SATURN SECOND LARGEST MOON IN THE
SOLAR SYSTEM (AFTER GANYMEDE) SURFACE TEMPERATURE IS 93 K (-
180oC OR -290oF)–NOT AS MUCH TIDAL HEATING AS
JUPITER'S LARGE MOONS–FARTHER FROM THE SUN THAN
JUPITER AND ITS MOONS ROCKY CORE SURROUNDED BY ICY
MANTLE? (H20, CH4 AND NH3 ICES)
TITAN HAS A THICK ATMOSPHERE
– 90% N2, ALSO Ar (ARGON), CH4 (METHANE), C2H6 (ETHANE), AND MORE COMPLEX HYDROCARBONS (SMOG)
– HAZY CLOUDS OBSCURE SURFACE– 200 KM THICK– 1.5 x PRESSURE OF EARTH’S ATMOSPHERE– ONLY MOON IN THE SOLAR SYSTEM WITH A THICK
ATMOSPHERE
– PROBABLY CH4 (METHANE) AND NH
3 (AMMONIA)
BUBBLED OUT OF CRUST WHEN TITAN WAS YOUNG AND WARM, UV LIGHT FROM SUN CAUSED CHEMICAL REACTIONS TO PRODUCE OTHER MOLECULES
TITANHUYGENS PROBE LANDED ON SURFACE IN 2004FEW IMPACT CRATERSRIVERS AND LAKES OF LIQUID METHANE AND ETHANE•ONLY BODY BESIDES EARTH KNOWN TO HAVE LIQUID ON THE SURFACE
LIQUID METHANE/ETHANE RAINMETHANE CONTINUES TO LEAK INTO ATMOSPHERE
–ICE VOLCANOES OR SLOWER SUBLIMATION?“SAND” DUNES PRODUCED BY WIND
–“SAND” IS MADE OF PIECES OF HYDROCARBON ICE
NO EVIDENCE OF LIFE
LIFE ON TITAN? PLENTY OF ORGANIC MOLECULES ENERGY SOURCE?
– CHEMICAL REACTIONS IN ATMOSPHERE– ICE VOLCANOES?
PLENTY OF LIQUID METHANE AND ETHANE– RECALL THAT NEITHER OF THESE IS AS GOOD A
LIQUID SOLVENT AS WATER IS MAY BE A SUB-SURFACE OCEAN OF LIQUID
WATER AND AMMONIA LOW TEMPERATURE WOULD MEAN THAT
CHEMICAL REACTIONS, AND THUS METABOLIC RATES, ARE VERY SLOW
PROBABLY TOO COLD FOR LIFE, BUT INTERESTING ORGANIC CHEMISTRY
ENCELADUS SMALL TO MEDIUM-SIZED MOON OF SATURN MIXTURE OF ICE AND ROCK FEW IMPACT CRATERS SATURN'S TIDAL FORCE CAUSES INTERNAL
WARMING HAS ICE VOLCANOES
– SOME REGIONS NEAR THE SOUTH POLE ARE WARMER THAN THE REST OF THE SURFACE
– CRACKS IN ICY CRUST, MATERIAL CAN SPEW UP FROM BELOW
– FOUNTAINS OF ICE PARTICLES AND WATER VAPOR
– SOME ORGANIC MOLECULES FOUND
IAPETUS MEDIUM-SIZED MOON OF SATURN
HEAVILY CRATERED
LEADING HEMISPHERE IS DARK, TRAILING HEMISPHERE IS LIGHT
DARK MATERIAL IS ORGANIC
MAY BE COLLECTED FROM SPACE AS IAPETUS MOVES IN ITS ORBIT
TRITON LARGEST MOON OF NEPTUNE RETROGRADE ORBIT - PROBABLY CAPTURED
KUIPER BELT OBJECT INTERIOR OF ICE AND ROCK FEW IMPACT CRATERS SURFACE CONTAINS NITROGEN ICE AND
METHANE ICE ACTIVE SURFACE (ICE MAY COVER LAKES OR
OCEAN OF NITROGEN, METHANE, AMMONIA, AND/OR WATER?)
LIQUID GEYSERS OR ICE VOLCANOES OCCASIONALLY ERUPT
VERY THIN NITROGEN ATMOSPHERE PROBABLY WAY TOO COLD FOR LIFE