NSCI 314 LIFE IN THE COSMOS 9 - SEARCHING FOR LIFE IN OUR SOLAR SYSTEM: EARTH'S MOON (CONTINUED), MERCURY, AND VENUS

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1 NSCI 314 LIFE IN THE COSMOS 9 - SEARCHING FOR LIFE IN OUR SOLAR SYSTEM: EARTH'S MOON (CONTINUED), MERCURY, AND VENUS Dr. Karen Kolehmainen Department of Physics CSUSB

2 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.

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4 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.

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7 LIFE ON EARTH S MOON? ALMOST CERTAINLY NOT PROBLEMS: NO ATMOSPHERE (MASS OF MOON IS SO LOW THAT ITS 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 IF THERE WERE AN ATMOSPHERE, IT WOULD SPREAD HEAT AROUND AND PREVENT TEMPERATURE EXTREMES

8 MERCURY g DIAMETER: 38% EARTH MASS: 5% EARTH DENSITY: 5.4 gm/cm³ SUNLIGHT: 6.5 X EARTH TEMP: 100 to 700 K (-170 to 430 oc or 280 to 800 of) ATMOSPHERE: NONE WATER: NONE SURFACE: ROCKY, HEAVILY CRATERED, NO CURRENT GEOLOGICAL ACTIVITY

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17 LIFE ON MERCURY? PROBABLY NOT PROBLEMS: NO ATMOSPHERE (MERCURY HAS TOO LOW A MASS, ITS GRAVITY CAN'T HOLD ONTO LIGHT GAS MOLECULES.) CONSEQUENCES: NO PROTECTION FROM UV BOMBARDMENT OR COSMIC RAYS LARGE TEMPERATURE EXTREMES NO AIR TO SPREAD HEAT AROUND (EXACERBATED BY SLOW ROTATION) NO WATER (OR ANY OTHER LIQUID THAT COULD SERVE AS A SOLVENT)

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19 LIFE ON MERCURY? SLOW ROTATION --> LARGE TEMPERATURE EXTREMES DAY AND NIGHT LAST 3 MONTHS EACH NO WATER ON SURFACE WITHOUT AN ATMOSPHERE, IT WOULD BOIL INTO SPACE SUB-SURFACE WATER (INSIDE ROCK)? MERCURY MAY HAVE SUFFERED A LARGE IMPACT THAT REMOVED VOLATILE MATERIALS LIKE WATER FROM THE ROCK ICE IN CRATER BOTTOMS NEAR POLES? COULD SURVIVE IN DEEP CRATERS WHERE SUNLIGHT NEVER REACHES THE BOTTOM LIKE ON EARTH'S MOON

20 VENUS DIAMETER: 95% EARTH MASS: 82% EARTH DENSITY: 5.3 gm/cm³ SUNLIGHT: 2 X EARTH TEMP: 730 K (460 oc or 850 of), NOT MUCH VARIATION ATMOSPHERE: 97% CO2, 3% N2, 90 X EARTH PRESSURE, SULFURIC ACID CLOUDS WATER: NONE SURFACE: ROCKY, CRATERED, RECENT LAVA FLOWS, UNCLEAR WHETHER ANY CURRENT GEOLOGICAL ACTIVITY

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28 GREENHOUSE EFFECT g SUNLIGHT ABSORBED BY PLANET S SURFACE ENERGY RE-RADIATED FROM GROUND AS INFRARED INFRARED RADIATION ABSORBED BY ATMOSPHERIC GREENHOUSE GASES: CO2,H2O, CH4, 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 of) HOTTER - MARS 5K (OR 9 of)hotter - VENUS 400K (OR 720 of)hotter

29 WHY ISN T THE GREENHOUSE EFFECT MORE IMPORTANT ON EARTH? LIMESTONE ROCKS (CALCIUM CARBONATE OR CaCO3) FORMED IN OCEANS. MOST CO2 (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.

30 WHY IS THE GREENHOUSE EFFECT SO IMPORTANT ON VENUS? TEMPERATURE ON PRE-GREENHOUSE VENUS WOULD HAVE BEEN ~350 TO 400 K, JUST A LITTLE TOO HOT FOR LIQUID WATER THEREFORE ALL WATER ON VENUS EVAPORATED H20 VAPOR IS A GREENHOUSE GAS AND INCREASED TEMPERATURE FURTHER MOST H20 VAPOR WAS PHOTODISSOCIATED, H ESCAPED TO SPACE, O COMBINED WITH OTHER ELEMENTS. NO OCEANS NO CARBONATE ROCKS TO ABSORB CO2, SO IT REMAINS IN ATMOSPHERE

31 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) CORROSIVE ATMOSPHERE THERE IS A TINY CHANCE THAT LIFE BEGAN ON VENUS LONG AGO WHEN IT WAS COOLER. IF SO, EXTREMOPHILES COULD POSSIBLY SURVIVE IN THE ATMOSPHERE (~50 KM ABOVE GROUND WHERE THERE ARE LIQUID WATER DROPS).