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Astronomy 305/Frontiers in Astronomy Class web site: http://glast.sonoma.edu/~lynnc/courses/a305 Office: Darwin 329A and NASA E/PO (707) 664-2655 Best way to reach me: [email protected] 9/30/03 Prof. Lynn Cominsky 1 Astrobiology Questions (3 weeks) Is there life elsewhere in our Solar system? (Group 5) Are Earth-like planets common? (Group 6) Are we alone? (Group 7) 9/30/03 Prof. Lynn Cominsky 2 Is there life elsewhere in the solar system? What is life? Activity #1 In groups of 3-4 students, develop a common set of characteristics that can identify life Write these characteristics down on your worksheets Test your definition by asking 5-10 questions – one group thinks of something that is alive or not, and a second group asks them questions about the characteristics to see if they can correctly determine the answer NOTE: you cannot ask “Is it alive?” 9/30/03 Prof. Lynn Cominsky 3 Group 5 9/30/03 Prof. Lynn Cominsky 4 What is Life? Some good criteria: Has heritable traits that can be transferred Able to have a population that evolves and adapts to the external environment Uses energy to maintain an internal state Some pretty good criteria: Has a complex internal structure (icicles?) Has cell membranes or walls that create an internal environment (viruses?) Able to extract energy from the environment (fire?) 9/30/03 Prof. Lynn Cominsky 5 What is Life? Some not-so-good criteria: Moves independently (plants?) Takes in nutrients (fire?) Gives off energy (fire?) Produces waste products (fire, icicles?) Also on Earth, all life: Has Carbon-based chemistry Requires liquid water LIVING MATTER EVADES THE DECAY TO EQUILIBRIUM - Erwin Schrodinger (famous physicist) 9/30/03 Prof. Lynn Cominsky 6 What is life? Activity #2 Examine the three jars – you can smell and touch the contents, but do not taste them Now add hot water to cover the contents Record your observations on the worksheet Use your list of characteristics to determine if there is anything alive in jars 1, 2 or 3 How can you distinguish between a living and non-living chemical change? Refine your definition of life based on these activities and write it on your worksheet 9/30/03 Prof. Lynn Cominsky 7 Schrodinger on What is Life?: What is the characteristic feature of life? When is a piece of matter said to be alive? When it goes on 'doing something', moving, exchanging material with its environment, and so forth, and that for a much longer period than we would expect an inanimate piece of matter to 'keep going' under similar circumstances. When a system that is not alive is isolated or placed in a uniform environment, all motion usually comes to a standstill very soon as a result of various kinds of friction; 9/30/03 Prof. Lynn Cominsky 8 Schrodinger on What is Life? (cont’d) differences of electric or chemical potential are equalized, substances which tend to form a chemical compound do so, temperature becomes uniform by heat conduction. After that the whole system fades away into a dead, inert lump of matter. A permanent state is reached, in which no observable events occur. The physicist calls this the state of thermodynamical equilibrium, or of 'maximum entropy'. 9/30/03 Prof. Lynn Cominsky 9 Solar System diameter ~5.9 x 109 km 9/30/03 Prof. Lynn Cominsky 10 Solar System Relative sizes and order of planets Sun Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto 9/30/03 Prof. Lynn Cominsky 11 Solar System Planet Distance (103 km) Mercury Orbital Period Diameter (days) ( km) Mass Moons (kg) 57910 87.97 4,880 3.30e23 0 Venus 108200 224.70 12,104 4.869e24 0 Earth 149600 365.26 12,756 5.9736e24 1 Mars 227940 686.98 6,794 6.4219e23 2 Jupiter 778330 4332.71 142,984 1.900e27 61 Saturn 1429400 10759.50 120,536 5.68e26 31 Uranus 2870990 30685 51,118 8.683e25 21 Neptune 4504300 60190 49,532 1.0247e26 11 Pluto 90800 2274 1.27e22 1 9/30/03 5913520 Prof. Lynn Cominsky 12 Solar System habitability factors • Liquid water (geothermal or atmospheric cycles) • Nutrients (chemicals, vitamins, minerals, fertilizers) • Energy source (light, food, carbohydrates, fats, sugars) • Temperature range (–15o C to +115o C on Earth) • Protection (look what happened to the dinosaurs!) • Light (or other source of heat or energy) 9/30/03 Prof. Lynn Cominsky 13 Mercury Highly eccentric orbit (used to test GR) Rotates 3 times in every 2 years Great temperature variations on surface -183oC (dark side) – 252oC (sun side) Very thin atmosphere Low magnetic field No water Many craters 9/30/03 Prof. Lynn Cominsky 14 Venus Brightest object in sky (except Sun and Moon) 1 day on Venus = 243 days on Earth Greenhouse effect raises surface temperature to 464oC (hotter than Mercury) Thick carbon dioxide atmosphere with sulfuric acid clouds No surface water, few craters Lava flows from volcanoes 9/30/03 Magellan Radar image Prof. Lynn Cominsky 15 Earth 71% of the surface is covered with liquid water Atmosphere of 77% nitrogen, 21% oxygen Greenhouse effect from small amount of carbon dioxide raises the surface temperature to 14oC Active surface due to plate tectonics earthquakes and volcanoes Mantle and crust mostly silicon compounds Few craters 9/30/03 Prof. Lynn Cominsky 16 Earth’s Moon (Luna) Lunar Prospector mission discovered ice at both poles No atmosphere -153oC to 107oC Receives same amount of sunlight as Earth, has same chemical makeup 9/30/03 Prof. Lynn Cominsky 17 Mars Being explored by Global Surveyor and 2001 Mars Odyssey Average temperature –63oC Varied terrain, mountains, canyons and craters Erosion indicates water used to be present Similar to Earth chemically No active volcanoes Very thin CO2 atmosphere Little oxygen Iron and sulfur core 9/30/03 Prof. Lynn Cominsky 18 Mars Panoramic view from Pathfinder Permanent CO2 ice caps with some water ice Weak sunlight Large dust storms 9/30/03 Prof. Lynn Cominsky 19 Life on Mars? “Face on Mars” Mars Global Surveyor Image April 2001 1976 Viking View 9/30/03 Prof. Lynn Cominsky 20 Life on Mars? Martian Meteorite Found in Antarctica in 1984 but origin is Mars Left Mars 16 million years ago, arrived in Antarctica 13,000 years ago Evidence of water infiltration while on Mars Carbonite mineral globules contain shapes that could be dead, fossilized bacteria and their byproducts Meteorite 9/30/03 Carbonate Globules Prof. Lynn Cominsky Fossilized Shapes 21 Meteorites Most meteorites are chunks of asteroids, the Moon or Mars; some are from comets >50 billion meteorites have traveled between Earth and Mars since the birth of the solar system Panspermia = Life comes from space Some think meteorites could have carried life from Mars to Earth or vice versa 9/30/03 Prof. Lynn Cominsky meteor 22 Jupiter Giant gas planet: 75% hydrogen, 25% helium Four largest moons known since 1610 (Galileo): Io, Europa Ganymede and Callisto Spacecraft exploration since 1973, Galileo is still in orbit around Jupiter Liquid metallic hydrogen mantle Possible hot, rocky core High velocity winds driven by internal heat 9/30/03 Prof. Lynn Cominsky 23 Jupiter Great Red Spot is lightning storm, with higher pressure Temperature from –200oC at cloud tops to thousands of degrees in interior Huge magnetic field 9/30/03 Prof. Lynn Cominsky 24 Jupiter’s Moon: Io Prometheus erupting • Youngest surface in Solar System • Many active volcanoes, sulfur • Temperature –150oC to 1250oC • No known water • Sulfur crust • No atmosphere Prometheus volcano 9/30/03 Prof. Lynn Cominsky 25 Jupiter’s Moon: Europa • Thin outer layer of water ice (1-10 km thick) • Possible liquid water ocean underneath the surface •No atmosphere • Volcanic activity under ocean? •Sulfur dust from Io’s eruptions on surface 9/30/03 Prof. Lynn Cominsky 26 Jupiter’s Moon: Ganymede • Rock and water ice on surface • No atmosphere • Average noon temperature –121oC on equator 9/30/03 Prof. Lynn Cominsky 27 Jupiter’s Moon: Callisto • Ice-rock mix throughout • Possible salt water underneath the surface •No atmosphere •Average temperature –108oC on equator 9/30/03 Prof. Lynn Cominsky 28 Saturn Giant gas planet: 75% hydrogen, 25% helium Oblate, flattened appearance, with bright rings Three spacecraft visits since 1979, Cassini is on its way, will arrive in 2004 Least dense planet, density is less than water Hot rocky core, liquid hydrogen Bands less visible than Jupiter; also has spots Very thin rings Rings mostly water ice Strong magnetic field 9/30/03 Prof. Lynn Cominsky 29 Saturn’s moon Titan Average surface temperature –179oC Water icebergs in an ocean of methane? 95% nitrogen, 5% methane atmosphere Pressure about 1.5 times Earth’s atmosphere No water in atmosphere Dim sunlight Will be visited by Huygens probe dropped from Cassini 9/30/03 Prof. Lynn Cominsky 30 Uranus Gas giant, mostly hydrogen atmosphere Looks blue due to methane in atmosphere Discovered by Herschel in 1781 Visited by Voyager 2 in 1986 HST image of Uranus’ pole points toward Sun Uranus and its rings Rock and ice, only 15% hydrogen No rocky core evident Clouds and color changes 11 known rings Extremely tilted magnetic field 20+ moons, 5 are rather large 9/30/03 Prof. Lynn Cominsky 31 Neptune Discovered in 1846 after being predicted from perturbations in Uranus’ orbit Visited by Voyager 2 in 1989 Composition similar to Uranus HST image of Internal heat source Neptune Strong winds and storms Great dark spot in 1989, not seen by HST in 1994 3 Dark rings seen by Voyager 2 Tilted magnetic field 8 known moons, Triton is large 9/30/03 Prof. Lynn Cominsky 32 Pluto Smallest planet and furthest from Sun (usually) Smaller than 7 moons in our solar system Discovered in 1930 by Clyde Tombaugh Orbit crosses inside Neptune No spacecraft observations Pluto and Charon Is Pluto really a planet? YES: It has a moon named Charon NO: It resembles asteroids NO: It has an elliptical orbit Rock and ice, little atmosphere 9/30/03 Prof. Lynn Cominsky 33 Cratering Mercury and the Moon show the results of bombardment during early formation of solar system Moon Mercury 9/30/03 Prof. Lynn Cominsky 34 Earth’s Surface Q: Why does the Earth’s surface show little evidence of cratering? Bombardment of Earth was similar to that of the Moon, Venus, Mars and Mercury A: Earth’s surface is actively reforming due to volcanic activity, erosion from water, plate tectonics,etc. 9/30/03 Prof. Lynn Cominsky 35 Volcanic Activity Io Jupiter’s Moon) shows volcanic activity Venus also has lava flows Prometheus volcano on Io Magellan Radar image of Venus 9/30/03 Prof. Lynn Cominsky 36 Erosion and Water Erosion (most likely due to liquid water) also seems to have affected Mars, which also has mountains and craters Moon has frozen water at poles but no signs of erosion Mars 9/30/03 Prof. Lynn Cominsky 37 Where is the Water? Europa (Jupiter’s Moon) thin outer layer of water ice (1-10 km thick) possible liquid water ocean underneath the surface Callisto (Jupiter’s Moon) • Ice-rock mix throughout • Possible salt water underneath surface 9/30/03 Prof. Lynn Cominsky 38 Where is the Water? Saturn Rings are mostly water ice Will be studied by Cassini in 2004 Titan (Saturn’s Moon) Water icebergs in an ocean of methane? No water in atmosphere Huygens probe will be dropped from Cassini 9/30/03 Prof. Lynn Cominsky 39 Planetary Missions MESSENGER (MErcury Surface, Space ENvironment, GEochemistry and Ranging), being built for launch April 2004, arrives at Mercury in 2009 Venus program – no current plans Galileo mission is now over. It flew by Io on 1/17/02, and by Amalthea on 11/05/02. It is due to plunge into the Jovian atmosphere on September 21, 2003. 9/30/03 Prof. Lynn Cominsky 40 Mars – 5 spacecraft on their way! Pathfinder (1996) Global Surveyor (1999) then two disasters. Two NASA landers (Spirit and Opportunity) are on their way to Mars, due to land on January 4 & 25, 2004. Europeans: Mars Express orbiter and Beagle 2 lander – due to arrive 12/26/03 Japanese orbiter (launched in 1998) will arrive at Mars in January 2004. 9/30/03 Prof. Lynn Cominsky 41 Spirit and Opportunity Entry movie Launch movie Exploration movie 9/30/03 Prof. Lynn Cominsky 42 Planetary Missions Europa orbiter – approved then eliminated in FY03 budget. Officially “under study.” Cassini mission to Saturn arrives July 2004. Will drop an ESA probe (Huygens) onto Titan, and flyby Titan and three smaller moons. Pluto/Kuiper Express – Preliminary designs under consideration. Possible launch in 2006, to arrive 2015-2017. 9/30/03 Prof. Lynn Cominsky 43 What makes a world habitable? In groups of 3-4, take a set of cards that summarize the properties of various solar system bodies Consider the following: Temperature Water Atmosphere Energy Nutrients What does life need? What kinds of conditions might limit life? Select your top three candidates for life 9/30/03 Prof. Lynn Cominsky 44 Web Resources Nine Planets tour http://www.seds.org/nineplanets/nineplanets Martian Meteorite http://www.lpi.usra.edu/lpi/meteorites/mars_ meteorite.html Solar System missions http://solarsystem.jpl.nasa.gov/missions/ Schrodinger: http://dieoff.org/page150.htm 9/30/03 Prof. Lynn Cominsky 45