1. NSCI 314 LIFE IN THE COSMOS 8 – SEARCHING FOR LIFE IN OUR SOLAR SYSTEM - GENERAL CONSIDERATIONS - LIFE ON THE INNER PLANETS? Dr. Karen Kolehmainen Department of Physics CSUSB http://physics.csusb.edu/~karen/

2. HOW TO SEARCH FOR LIFE WITHIN OUR SOLAR SYSTEM OBSERVATIONS WITH TELESCOPES, ETC. –LIGHT-GATHERING (MAKE FAINT OBJECTS BRIGHTER) –MAGNIFY OR ENLARGE IMAGE –PICK OUT DETAILS IN IMAGE (IMPROVE RESOLUTION) –CAN USE A VARIETY OF WAVELENGTHS (NOT JUST VISIBLE LIGHT) –CAN DO SPECTROSCOPIC ANALYSIS SPLIT LIGHT INTO COLORS ANALYZE BRIGHTNESS AT VARIOUS WAVELENGTHS INDICATES PRESENCE OF VARIOUS MATERIALS VISITS BY SPACECRAFT –FLYBY (ALL PLANETS, PLUS MANY MOONS) –ORBITER (EARTH'S MOON, VENUS, MARS, JUPITER, SATURN) –PROBE DESCENDS INTO ATMOSPHERE (JUPITER) –LANDER (EARTH'S MOON, VENUS, MARS, SATURN'S MOON TITAN) –SAMPLE RETURN (EARTH'S MOON) –HUMAN VISITS (EARTH'S MOON)

3. TO ESTIMATE HOW EASY IT WOULD BE FOR US TO FIND LIFE (IF IT EXISTS) ON ANOTHER PLANET IN OUR SOLAR SYSTEM, TURN THE QUESTION AROUND: HOW COULD A HYPOTHETICAL ALIEN CIVILIZATION (WITH TECHNOLOGY SIMILAR TO OURS) ON A NEARBY PLANET (IN OUR SOLAR SYSTEM) TELL THERE IS LIFE ON EARTH? –SPECTROSCOPIC DETECTION OF GASES IN THE ATMOSPHERE THAT ARE PRODUCED BY LIVING ORGANISMS: OXYGEN AND MAYBE METHANE –INFRARED OBSERVATIONS CAN DETECT SEASONAL CHANGES IN VEGETATION (DIFFICULT)

4. HOW COULD AN ALIEN ON A NEARBY PLANET TELL THERE IS A TECHNOLOGICALLY ADVANCED CIVILIZATION ON EARTH? LIGHTS FROM CITIES VISIBLE AT NIGHT TV AND FM RADIO BROADCASTS ESCAPE INTO SPACE SPECTROSCOPIC DETECTION OF GASES IN THE ATMOSPHERE THAT ARE PRODUCED BY TECHNOLOGY (e.g., CFCs)

5. EXTRATERRESTRIAL LIFE IN OUR SOLAR SYSTEM? NEED: ELEMENTS LIKE CARBON (OR SILICON?), HYDROGEN, OXYGEN, NITROGEN –ENOUGH ALMOST EVERYWHERE SIMPLE ORGANIC MOLECULES –PROBABLY ENOUGH IN MANY LOCATIONS SOURCE OF ENERGY –SUNLIGHT (MORE AVAILABLE CLOSER TO SUN) –HEAT FROM INSIDE PLANET OR MOON –CHEMICAL SOURCES PROTECTED ENVIRONMENT –ATMOSPHERE –OCEANS –UNDERGROUND LIQUID SOLVENT (WATER OR SOMETHING ELSE?) –REQUIRES CORRECT TEMPERATURE RANGE

6. WHAT SHOULD A LIQUID SOLVENT DO? MUST BE ABUNDANT MUST BE ABLE TO DISSOLVE A LOT OF DIFFERENT MATERIALS IN IT SHOULD REMAIN LIQUID OVER A LARGE TEMPERATURE RANGE TEMPERATURE RANGE OVER WHICH SOLVENT IS LIQUID SHOULDN’T BE TOO HIGH OR TOO LOW –IF TEMPERATURE RANGE IS TOO LOW, INTERACTIONS PROCEED TOO SLOWLY –IF TEMPERATURE RANGE IS TOO HIGH, MOLECULES ARE BROKEN APART TOO EASILY MIGHT BE BENEFICIAL IF IT HELPS ORGANISMS REGULATE THEIR INTERNAL TEMPERATURE

7. SPECIFIC AND LATENT HEAT SPECIFIC HEAT = THE AMOUNT OF ENERGY THAT NEEDS TO BE ADDED TO 1 GRAM OF MATERIAL TO RAISE ITS TEMPERATURE BY 1 o C LATENT HEAT OF VAPORIZATION = THE AMOUNT OF HEAT THAT NEEDS TO BE ADDED TO BOIL ONE GRAM OF LIQUID MATERIAL (ASSUMING IT IS ALREADY AT THE APPROPRIATE TEMPERATURE, i.e., THE “BOILING POINT”) SPECIFIC HEAT AND LATENT HEAT ARE DIFFERENT FOR DIFFERENT MATERIALS

8. SPECIFIC AND LATENT HEAT A MATERIAL WITH A LARGE SPECIFIC HEAT DOESN’T UNDERGO EXTREME VARIATIONS IN TEMPERATURE. SINCE LARGE AMOUNTS OF ENERGY MUST BE ADDED (REMOVED) TO INCREASE (DECREASE) THE TEMPERATURE VERY MUCH, THE TEMPERATURE DOESN'T CHANGE MUCH. IF A LIQUID WITH A LARGE LATENT HEAT EVAPORATES, IT CARRIES A LOT OF HEAT AWAY WITH IT. IF A LIQUID SOLVENT HAS A LARGE SPECIFIC HEAT AND A LARGE LATENT HEAT, ORGANISMS THAT USE IT WILL BE ABLE TO MAINTAIN A CONSTANT TEMPERATURE MORE EASILY.

9. ADVANTAGES OF WATER ABUNDANT (2 ND MOST COMMON MOLECULE IN INTERSTELLAR SPACE) DISSOLVES MANY MATERIALS (BECAUSE H 2 O MOLECULE IS “POLAR”) STAYS LIQUID OVER A LARGE TEMPERATURE RANGE VERY LARGE SPECIFIC HEAT AND LATENT HEAT – KEEPS TEMPERATURE FROM VARYING TOO MUCH LARGE SURFACE TENSION – DROPS FORM EASILY, MAY BE IMPORTANT FOR THE ORIGIN OF LIFE (FORMATION OF CELL MEMBRANES)

10. ADVANTAGES OF WATER EXPANSION UPON FREEZING –COULD BE AN ADVANTAGE BECAUSE: ICE FLOATS ON LIQUID WATER THIS PREVENTS BODIES OF WATER FROM FREEZING OVER COMPLETELY, WHICH WOULD KILL ORGANISMS THERE –COULD BE A DISADVANTAGE BECAUSE: CELLS RUPTURE WHEN THEY FREEZE –COULD BE NEUTRAL IF TEMPERATURE NEVER GETS LOW ENOUGH FOR FREEZING

11. OTHER SOLVENTS? CONSIDER AMMONIA (NH 3 ), METHANE (CH 4 ), AND ETHANE (C 2 H 6 ): –ALL ARE RELATIVELY ABUNDANT. –NOT POLAR MOLECULES - CAN’T DISSOLVE AS MANY MATERIALS AS WATER. –LOW SURFACE TENSION - HARDER TO FORM DROPS. –ETHANE IS LIQUID OVER A LARGE TEMPERATURE RANGE, METHANE AND AMMONIA ARE NOT. –ALL ARE LIQUID AT LOW TEMPERATURES (LOWER THAN WATER) – METABOLIC PROCESSES WOULD BE SLOW. –SMALL LATENT HEAT AND/OR SPECIFIC HEAT (EXCEPT AMMONIA). –NONE EXPAND UPON FREEZING. MOST OTHER POSSIBLE LIQUID SOLVENTS AREN’T VERY ABUNDANT.

12. INNER (TERRESTRIAL) PLANETS MERCURY, VENUS, EARTH & MARS WARMER, CLOSER TO SUN RELATIVELY LOW MASS DENSE, ROCKY, FEW LIGHT ELEMENTS FEW OR NO MOONS NO RINGS

13. OUTER (JOVIAN) PLANETS JUPITER, SATURN, URANUS, NEPTUNE COLDER, FARTHER FROM SUN HIGH MASS LOW DENSITY, MOSTLY GASEOUS, LOTS OF LIGHT ELEMENTS LOTS OF MOONS (LIKE MINIATURE SOLAR SYSTEMS) ALL HAVE RINGS

14. CHARACTERISTICS OF PLANETS Planet Diameter (Earth=1) Mass (Earth=1) Average Density (gm/cm³) Orbital Period (Years) Distance From the Sun (AU or Earth=1) Mercury Venus Earth Mars [Asteroids] Jupiter Saturn Uranus Neptune 0.38 0.95 1.00 0.53 - 11.2 9.5 4.0 3.9 0.06 0.81 1.00 0.11 - 318 95 15 17 5.4 5.3 5.5 4.0 - 1.3 0.7 1.3 1.6 0.24 0.62 1.00 1.88 - 12 29 84 165 0.39 0.72 1.00 1.52 [Avg. = 2.77] 5.2 9.5 19 30

15. 1. FLAT SHAPE (PLANETARY ORBITS ARE IN THE SAME PLANE) EXPLAINED BY CONSERVATION OF ANGULAR MOMENTUM NEBULA FLATTENS AS IT CONTRACTS 2. COMMON DIRECTION OF PLANETARY ORBITAL MOTION, MOST PLANETS’ ROTATIONS, & ORBITS OF MOST MOONS EXPLAINED BY CONSERVATION OF ANGULAR MOMENTUM DIRECTION OF ROTATION IS THE SAME AS THAT OF ORIGINAL NEBULA 3. ORIGIN OF COMETS AND ASTEROIDS LEFTOVER PLANETESIMALS THAT DIDN'T GET INCORPORATED INTO PLANETS 1. SOLAR SYSTEM PROPERTIES AS EXPLAINED BY THE NEBULAR THEORY OF FORMATION

16. 1. - OUTER PLANETS ARE MUCH LARGER AND MORE MASSIVE THAN INNER PLANETS. 2. - INNER PLANETS ARE MADE OF ROCKY MATERIALS. 3. - OUTER PLANETS ARE MADE MOSTLY OF GAS. 4. - MOONS OF OUTER PLANETS ARE MADE MOSTLY OF ICE. FAST-MOVING GAS MOLECULES ESCAPED THE GRAVITY OF PLANETS IN THE HOTTER INNER SOLAR NEBULA. SLOWER MOVING GAS PARTICLES WEREN'T ABLE TO ESCAPE THE GRAVITY OF PLANETS IN THE COOLER OUTER NEBULA. ICE PARTICLES CONDENSED IN THE COOL OUTER NEBULA, BUT IT WAS TOO HOT IN THE INNER NEBULA. 5. - ALSO RECALL THAT LARGER PLANETS AND MOONS COOL MORE SLOWLY THAN SMALL ONES, AND THEREFORE ARE STILL HOTTER INSIDE. 1. SOLAR SYSTEM PROPERTIES AS EXPLAINED BY THE NEBULAR THEORY OF FORMATION - DIFFERENCES BETWEEN INNER AND OUTER PLANETS

17. LOOSE ENDS PLUTO AND NEW “PLANET” (AND THEIR MOONS) ARE MOST PROPERLY THOUGHT OF AS KUIPER BELT OBJECTS SEVERAL MOONS ARE PROBABLY CAPTURED KUIPER BELT OBJECTS –TRITON (NEPTUNE) – RETROGRADE ORBIT SEVERAL MOONS ARE PROBABLY CAPTURED ASTEROIDS –PHOBOS AND DEIMOS (MARS) EVIDENCE OF COLLISIONS –ORIGIN OF EARTH'S MOON EVIDENCE OF NEAR-COLLISIONS –VENUS HAS RETROGRADE ROTATION –URANUS’ ROTATION AXIS IS TIPPED SIDEWAYS

18. COMETS “DIRTY SNOWBALLS” – WATER ICE, CO 2 ICE, SIMPLE ORGANIC MOLECULES NUCLEUS IS A FEW KM TO A FEW HUNDRED KM ACROSS, IRREGULARLY SHAPED MOST ORBITS ARE HIGHLY ELLIPTICAL – VERY CLOSE TO SUN AT ONE END & VERY FAR FROM SUN AT THE OTHER END ORBITS CAN BE IN ANY PLANE LEFTOVER ICY PLANETESIMALS FROM FORMATION OF SOLAR SYSTEM

19. SOURCES OF COMETS OORT CLOUD –SPHERICAL RESERVOIR OF COMETS –HUGE - RADIUS OF APPROXIMATELY 1 LY (60,000 AU) –PLANETESIMALS THAT WERE EJECTED OUTWARD –COMETS HERE CAN BE SHIFTED INTO NEW ORBITS BY PASSING STARS KUIPER BELT –SMALLER DISK-SHAPED RESERVOIR OF COMETS –RADIUS OF APPROXIMATELY 50 AU –INCLUDES PLUTO AND NEW “PLANET” AS LARGEST OBJECTS –PLANETESIMALS THAT WERE NOT EJECTED OUTWARD –COMETS HERE CAN BE SHIFTED INTO NEW ORBITS BY MASSIVE PLANETS NEW ORBIT CAN BRING COMET INTO INNER SOLAR SYSTEM, WHERE WE SEE IT

21. COMETS WHEN NEAR THE SUN ICE SUBLIMATES (SOLID  GAS), RELEASING DUST GRAINS FROM NUCLEUS RELEASED GAS & DUST FORM A CLOUD CALLED COMA (CAN BE LARGER THAN THE SUN) GAS IS IONIZED BY SUNLIGHT AND PUSHED DIRECTLY AWAY FROM SUN BY PRESSURE OF PHOTONS, FORMING BLUE GAS TAIL DUST LAGS BEHIND COMET IN ORBIT, FORMING YELLOWER DUST TAIL

22. ASTEROIDS ROCKY OBJECTS UP TO FEW HUNDRED KM ACROSS MOST ARE IRREGULARLY SHAPED, NOT SPHERICAL ORBIT THE SUN, MOST BETWEEN THE ORBITS OF MARS AND JUPITER LEFTOVER ROCKY PLANETESIMALS THAT DIDN’T FORM A PLANET (PROBABLY BECAUSE OF JUPITER’S GRAVITY)

23. METEORS, METEOROIDS, AND METEORITES METEOROIDS: SMALL ROCKY OBJECTS ORBITING THE SUN – SMALLER THAN ASTEROIDS METEORS: METEOROIDS THAT HAVE ENTERED EARTH’S ATMOSPHERE, USUALLY VAPORIZE DUE TO FRICTIONAL HEATING, “SHOOTING STARS” OR “FALLING STARS” METEORITES: METEORS THAT HAVE PARTIALLY SURVIVED ATMOSPHERIC PASSAGE AND HIT THE GROUND

24. METEORITES TYPES (BASED ON COMPOSITION): –METALLIC (IRON, NICKEL, ETC.) –STONY-IRON –STONY CARBONACEOUS CHONDRITES CARBONACEOUS CHONDRITES CONTAIN WATER AND ORGANIC COMPOUNDS, INCLUDING 74 AMINO ACIDS (50% L, 50% R), ALL 5 GENETIC BASES, FATTY ACIDS, ETC.

25. ADVANTAGES OF PLANETS AND LARGE MOONS FOR LIFE CONDUCIVE TO CHEMISTRY (ATOMS COMBINING AND RECOMBINING TO FORM MOLECULES) MANY PROVIDE A RELATIVELY STABLE AND PROTECTED ENVIRONMENT –ATMOSPHERE PROVIDES PROTECTION FROM UV AND OTHER HIGH ENERGY PHOTONS AND FROM COSMIC RAYS SMALL VARIATIONS IN ENVIRONMENT –TEMPERATURE VARIATIONS –POSSIBLE INTERFACES BETWEEN LAND, OCEANS, AND ATMOSPHERE

26. LIFE ON SOLAR SYSTEM BODIES OTHER THAN PLANETS & LARGE MOONS? SMALL MOONS, ASTEROIDS, COMETS, ETC.? –BIG PROBLEM: NO ATMOSPHERE TEMPERATURE EXTREMES BETWEEN DAY AND NIGHT NO LIQUIDS - THEY BOIL INTO SPACE NO UV PROTECTION SUN (OR STARS IN GENERAL)? –TOO HOT FOR COMPLEX MOLECULES TO FORM

27. INNER (TERRESTRIAL) PLANETS MERCURY, VENUS, EARTH & MARS WARMER, CLOSER TO SUN RELATIVELY LOW MASS DENSE, ROCKY, FEW LIGHT ELEMENTS FEW OR NO MOONS NO RINGS

28. EARTH  DIAMETER: 1 EARTH  MASS: 1 EARTH  DENSITY: 5.5 g/cm³  SUNLIGHT: 1 EARTH  TEMP: 210 to 320 K (-60 to 50 o C or –80 to 120 o F)  ATMOSPHERE: 78% N 2, 21% O 2, 1% Ar, 0.03% CO 2 ; H 2 0 CLOUDS  WATER: COVERS 71% OF SURFACE, BUT ONLY 0.02% OF TOTAL MASS, OCEANS 3.6 KM DEEP ON AVERAGE  SURFACE: ROCKY, WITH OCEANS, ICE CAPS, VOLCANOES, PLATE TECTONICS, LIFE TO ~5 KM DEPTH

33. EARTH’S MOON  DIAMETER: 27% EARTH  MASS: 1.2% EARTH  DENSITY: 3.3 g/cm³  SUNLIGHT: 1 EARTH  TEMP: 160 to 400 K (-110 to 130 o C or –170 to 260 o F)  ATMOSPHERE: NONE  WATER: NO LIQUID WATER, BUT PERMANENT ICE IN A FEW CRATERS NEAR THE POLES THAT NEVER GET SUNLIGHT  SURFACE: ROCKY, HEAVILY CRATERED, SMOOTHER MARIA (FORMED VIA LAVA FLOODING BASINS AFTER LARGE IMPACTS), NO CURRENT GEOLOGICAL ACTIVITY (COOL SOLID INTERIOR)

36. TIDAL FORCES THINK ABOUT THE GRAVITATIONAL FORCE OF THE MOON PULLING ON THE EARTH. THE SIDE OF THE EARTH THAT IS CLOSEST TO THE MOON EXPERIENCES A STRONGER FORCE THAN DOES THE SIDE OF THE EARTH THAT IS FARTHEST FROM THE MOON. THE DIFFERENCE BETWEEN THE FORCES ON DIFFERENT SIDES OF THE EARTH CAUSES TIDES. (OCEANS CAN ALTER SHAPE MORE EASILY THAN ROCK.) EARTH ROTATES INSIDE TIDAL BULGES, PRODUCING TWO HIGH TIDES PER DAY. FRICTION BETWEEN WATER AND OCEAN BOTTOM IS SLOWING DOWN EARTH’S ROTATION.

38. TIDAL FORCES EARTH ALSO EXERTS TIDAL FORCES ON THE MOON. THE MOON HAS NO OCEANS, BUT THE ROCK ITSELF IS DISTORTED INTO AN ELONGATED SHAPE. WHEN THE MOON FIRST FORMED, IT WAS ROTATING MORE QUICKLY. AS IT DID SO, THE TIDAL FORCES KEPT CHANGING THE MOON'S SHAPE. FRICTION SLOWED DOWN THE MOON’S ORIGINAL ROTATION UNTIL IT NOW ROTATES ONLY ONCE PER ORBIT. SYNCHRONOUS ROTATION: THE MOON NOW KEEPS ONE SIDE FACING THE EARTH. THIS HAS ALSO HAPPENED WITH MOST MOONS OF OUTER PLANETS.

41. MERCURY  DIAMETER: 38% EARTH  MASS: 5% EARTH  DENSITY: 5.4 gm/cm³  SUNLIGHT: 6.5 X EARTH  TEMP: 100 to 700 K (-170 to 430 o C or –280 to 800 o F)  ATMOSPHERE: NONE  WATER: NONE  SURFACE: ROCKY, HEAVILY CRATERED, NO CURRENT GEOLOGICAL ACTIVITY

44. LIFE ON EARTH’S MOON OR MERCURY? PROBABLY NOT PROBLEMS: – NO ATMOSPHERE (MASSES OF MOON AND MERCURY ARE SO LOW THAT THEIR GRAVITY CAN'T HOLD ONTO LIGHT GAS MOLECULES) NO PROTECTION FROM UV BOMBARDMENT OR COSMIC RAYS NO LIQUID WATER (OR ANY OTHER LIQUID THAT COULD SERVE AS A SOLVENT) LARGE TEMPERATURE EXTREMES (ESPECIALLY ON MERCURY)

45. VENUS  DIAMETER: 95% EARTH  MASS: 82% EARTH  DENSITY: 5.3 gm/cm³  SUNLIGHT: 2 X EARTH  TEMP: 730 K (460 o C or 850 o F), NOT MUCH VARIATION  ATMOSPHERE: 97% CO 2, 3% N 2, 90 X EARTH PRESSURE, SULFURIC ACID CLOUDS  WATER: NONE  SURFACE: ROCKY, CRATERED, RECENT LAVA FLOWS, UNCLEAR WHETHER ANY CURRENT GEOLOGICAL ACTIVITY

50. GREENHOUSE EFFECT  SUNLIGHT ABSORBED BY PLANET’S SURFACE  ENERGY RE-RADIATED FROM GROUND AS INFRARED  INFRARED ABSORBED BY ATMOSPHERIC GREENHOUSE GASES: CO 2,H 2 O, CH 4, OTHERS  ATMOSPHERE WARMS, RADIATES EXCESS HEAT TO SPACE (AS BLACKBODY)  EVENTUALLY EQUILIBRIUM IS REACHED SO THAT ENERGY ABSORBED = ENERGY RADIATED, AND TEMPERATURE STABILIZES - EARTH 40K (OR 72 o F) HOTTER - MARS 5K (OR 9 o F) HOTTER - VENUS 400K (OR 720 o F)HOTTER

51. WHY ISN’T THE GREENHOUSE EFFECT MORE IMPORTANT ON EARTH? LIMESTONE ROCKS (CALCIUM CARBONATE OR CaCO 3 ) FORMED IN OCEANS. MOST CO 2 (170,000 x MORE THAN IN OUR ATMOSPHERE) IS DISSOLVED IN SEA WATER AND LOCKED UP IN LIMESTONE. IF IT WEREN’T, GREENHOUSE EFFECT WOULD BE MUCH MORE SEVERE. HUMAN INDUSTRIAL ACTIVITY IS ADDING GREENHOUSE GASES TO ATMOSPHERE, RESULTING IN GLOBAL WARMING.

52. WHY IS THE GREENHOUSE EFFECT SO IMPORTANT ON VENUS? TEMPERATURE ON PRE-GREENHOUSE VENUS WOULD HAVE BEEN ~350 TO 400 K, TOO HOT FOR LIQUID WATER THEREFORE VENUS' WATER EVAPORATED, OCEANS NEVER FORMED H 2 0 VAPOR IS A GREENHOUSE GAS AND INCREASED TEMPERATURE FURTHER MOST H 2 0 WAS PHOTODISSOCIATED, H ESCAPED TO SPACE, O COMBINED WITH OTHER ELEMENTS NO OCEANS, THEREFORE NO CARBONATE ROCKS TO ABSORB CO 2, SO IT REMAINS IN ATMOSPHERE

53. LIFE ON VENUS? PROBABLY NOT PROBLEMS: – WAY TOO HOT DUE TO RUNAWAY GREENHOUSE EFFECT – NO LIQUID WATER (OR ANY OTHER LIQUID THAT COULD SERVE AS A SOLVENT) – ATMOSPHERIC PRESSURE VERY HIGH (ALTHOUGH NO HIGHER THAN AT SOME HYDROTHERMAL VENTS ON EARTH)