9/30/03Prof. Lynn Cominsky1 Class web site: Office: Darwin 329A and NASA E/PO (707) Best way to reach me: Astronomy 305/Frontiers in Astronomy

9/30/03Prof. Lynn Cominsky2 Astrobiology Questions (3 weeks) Is there life elsewhere in our Solar system? (Group 5) Is there life elsewhere in our Solar system? (Group 5) Are Earth-like planets common? (Group 6) Are Earth-like planets common? (Group 6) Are we alone? (Group 7) Are we alone? (Group 7)

9/30/03Prof. Lynn Cominsky3 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 In groups of 3-4 students, develop a common set of characteristics that can identify life Write these characteristics down on your worksheets 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 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?” NOTE: you cannot ask “Is it alive?”

9/30/03Prof. Lynn Cominsky4 Group 5

9/30/03Prof. Lynn Cominsky5 What is Life? Some good criteria: Some good criteria: Has heritable traits that can be transferred Has heritable traits that can be transferred Able to have a population that evolves and adapts to the external environment Able to have a population that evolves and adapts to the external environment Uses energy to maintain an internal state Uses energy to maintain an internal state Some pretty good criteria: Some pretty good criteria: Has a complex internal structure (icicles?) Has a complex internal structure (icicles?) Has cell membranes or walls that create an internal environment (viruses?) Has cell membranes or walls that create an internal environment (viruses?) Able to extract energy from the environment (fire?) Able to extract energy from the environment (fire?)

9/30/03Prof. Lynn Cominsky6 What is Life? Some not-so-good criteria: Some not-so-good criteria: Moves independently (plants?) Moves independently (plants?) Takes in nutrients (fire?) Takes in nutrients (fire?) Gives off energy (fire?) Gives off energy (fire?) Produces waste products (fire, icicles?) Produces waste products (fire, icicles?) Also on Earth, all life: Also on Earth, all life: Has Carbon-based chemistry Has Carbon-based chemistry Requires liquid water Requires liquid water LIVING MATTER EVADES THE DECAY TO EQUILIBRIUM - Erwin Schrodinger (famous physicist)

9/30/03Prof. Lynn Cominsky7 What is life? Activity #2 Examine the three jars – you can smell and touch the contents, but do not taste them Examine the three jars – you can smell and touch the contents, but do not taste them Now add hot water to cover the contents Now add hot water to cover the contents Record your observations on the worksheet Record your observations on the worksheet Use your list of characteristics to determine if there is anything alive in jars 1, 2 or 3 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? 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 Refine your definition of life based on these activities and write it on your worksheet

9/30/03Prof. Lynn Cominsky8 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; 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;

9/30/03Prof. Lynn Cominsky9 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'. 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'.

9/30/03Prof. Lynn Cominsky10 Solar System diameter ~5.9 x 10 9 km

9/30/03Prof. Lynn Cominsky11 Solar System Relative sizes and order of planets Sun Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto

9/30/03Prof. Lynn Cominsky12 Planet Distance Orbital Period Diameter Mass Moons (10 3 km) (days) ( km) (kg) Mercury , e23 0 Venus , e24 0 Earth , e24 1 Mars , e23 2 Jupiter , e27 61 Saturn , e26 31 Uranus , e25 21 Neptune , e26 11 Pluto e22 1 Solar System

9/30/03Prof. Lynn Cominsky13 Solar System habitability factors Temperature range (–15 o C to +115 o C on Earth) Protection (look what happened to the dinosaurs!) Light (or other source of heat or energy) Liquid water (geothermal or atmospheric cycles) Nutrients (chemicals, vitamins, minerals, fertilizers) Energy source (light, food, carbohydrates, fats, sugars)

9/30/03Prof. Lynn Cominsky14 Mercury Highly eccentric orbit (used to test GR) Highly eccentric orbit (used to test GR) Rotates 3 times in every 2 years Rotates 3 times in every 2 years Great temperature variations on surface Great temperature variations on surface -183 o C (dark side) – 252 o C (sun side) -183 o C (dark side) – 252 o C (sun side) Very thin atmosphere Very thin atmosphere Low magnetic field Low magnetic field No water No water Many craters Many craters

9/30/03Prof. Lynn Cominsky15 Venus Brightest object in sky (except Sun and Moon) Brightest object in sky (except Sun and Moon) 1 day on Venus = 1 day on Venus = 243 days on Earth 243 days on Earth Greenhouse effect raises surface temperature to 464 o C (hotter than Mercury) Greenhouse effect raises surface temperature to 464 o C (hotter than Mercury) Thick carbon dioxide atmosphere with sulfuric acid clouds Thick carbon dioxide atmosphere with sulfuric acid clouds No surface water, few craters No surface water, few craters Lava flows from volcanoes Lava flows from volcanoes Magellan Radar image

9/30/03Prof. Lynn Cominsky16 Earth 71% of the surface is covered with liquid water 71% of the surface is covered with liquid water Atmosphere of 77% nitrogen, 21% oxygen Atmosphere of 77% nitrogen, 21% oxygen Greenhouse effect from small amount of carbon dioxide raises the surface temperature to 14 o C Greenhouse effect from small amount of carbon dioxide raises the surface temperature to 14 o C Active surface due to plate tectonics  earthquakes and volcanoes Active surface due to plate tectonics  earthquakes and volcanoes Mantle and crust mostly silicon compounds Mantle and crust mostly silicon compounds Few craters Few craters

9/30/03Prof. Lynn Cominsky17 Earth’s Moon (Luna) Lunar Prospector mission Lunar Prospector mission discovered ice at both poles No atmosphere No atmosphere -153 o C to 107 o C -153 o C to 107 o C Receives same amount of sunlight as Earth, has same chemical makeup Receives same amount of sunlight as Earth, has same chemical makeup

9/30/03Prof. Lynn Cominsky18 Mars Being explored by Global Surveyor and 2001 Mars Odyssey Being explored by Global Surveyor and 2001 Mars Odyssey Average temperature –63 o C Average temperature –63 o C Varied terrain, mountains, canyons and craters Varied terrain, mountains, canyons and craters Erosion indicates water used to be present Erosion indicates water used to be present Similar to Earth chemically Similar to Earth chemically No active volcanoes No active volcanoes Very thin CO 2 atmosphere Very thin CO 2 atmosphere Little oxygen Little oxygen Iron and sulfur core Iron and sulfur core

9/30/03Prof. Lynn Cominsky19 Mars Permanent CO 2 ice caps with some water ice Permanent CO 2 ice caps with some water ice Weak sunlight Weak sunlight Large dust storms Large dust storms Panoramic view from Pathfinder

9/30/03Prof. Lynn Cominsky20 Life on Mars? “Face on Mars” “Face on Mars” 1976 Viking View Mars Global Surveyor Image April 2001

9/30/03Prof. Lynn Cominsky21 Life on Mars? Martian Meteorite Found in Antarctica in 1984 but origin is Mars Found in Antarctica in 1984 but origin is Mars Left Mars 16 million years ago, arrived in Antarctica 13,000 years ago Left Mars 16 million years ago, arrived in Antarctica 13,000 years ago Evidence of water infiltration while on Mars Evidence of water infiltration while on Mars Carbonite mineral globules contain shapes that could be dead, fossilized bacteria and their byproducts Carbonite mineral globules contain shapes that could be dead, fossilized bacteria and their byproducts MeteoriteCarbonate GlobulesFossilized Shapes

9/30/03Prof. Lynn Cominsky22 Meteorites Most meteorites are chunks of asteroids, the Moon or Mars; some are from comets 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 >50 billion meteorites have traveled between Earth and Mars since the birth of the solar system Panspermia = Life comes from space Panspermia = Life comes from space Some think meteorites could have carried life from Mars to Earth or vice versa Some think meteorites could have carried life from Mars to Earth or vice versa meteor

9/30/03Prof. Lynn Cominsky23 Jupiter Giant gas planet: 75% hydrogen, 25% helium Giant gas planet: 75% hydrogen, 25% helium Four largest moons known since 1610 (Galileo): Four largest moons known since 1610 (Galileo): Io, Europa Ganymede and Callisto Spacecraft exploration since 1973, Galileo is still in orbit around Jupiter Spacecraft exploration since 1973, Galileo is still in orbit around Jupiter Liquid metallic hydrogen mantle Liquid metallic hydrogen mantle Possible hot, rocky core Possible hot, rocky core High velocity winds High velocity winds driven by internal heat

9/30/03Prof. Lynn Cominsky24 Jupiter Great Red Spot is lightning storm, with higher pressure Great Red Spot is lightning storm, with higher pressure Temperature from –200 o C at cloud tops to thousands of degrees in interior Temperature from –200 o C at cloud tops to thousands of degrees in interior Huge magnetic field Huge magnetic field

9/30/03Prof. Lynn Cominsky25 Jupiter’s Moon: Io Youngest surface in Solar System Many active volcanoes, sulfur Temperature –150 o C to 1250 o C No known water Sulfur crust No atmosphere Prometheus volcano Prometheus erupting

9/30/03Prof. Lynn Cominsky26 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

9/30/03Prof. Lynn Cominsky27 Jupiter’s Moon: Ganymede Rock and water ice on surface No atmosphere Average noon temperature –121 o C on equator

9/30/03Prof. Lynn Cominsky28 Jupiter’s Moon: Callisto Ice-rock mix throughout Possible salt water underneath the surface No atmosphere Average temperature –108 o C on equator

9/30/03Prof. Lynn Cominsky29 Saturn Giant gas planet: 75% hydrogen, 25% helium Giant gas planet: 75% hydrogen, 25% helium Oblate, flattened appearance, with bright rings Oblate, flattened appearance, with bright rings Three spacecraft visits since 1979, Cassini is on its way, will arrive in 2004 Three spacecraft visits since 1979, Cassini is on its way, will arrive in 2004 Least dense planet, density is less than water Least dense planet, density is less than water Hot rocky core, liquid hydrogen Hot rocky core, liquid hydrogen Bands less visible than Bands less visible than Jupiter; also has spots Very thin rings Very thin rings Rings mostly water ice Rings mostly water ice Strong magnetic field Strong magnetic field

9/30/03Prof. Lynn Cominsky30 Saturn’s moon Titan Average surface temperature –179 o C Average surface temperature –179 o C Water icebergs in an ocean of methane? Water icebergs in an ocean of methane? 95% nitrogen, 5% methane atmosphere 95% nitrogen, 5% methane atmosphere Pressure about 1.5 times Pressure about 1.5 times Earth’s atmosphere No water in atmosphere No water in atmosphere Dim sunlight Dim sunlight Will be visited by Huygens Will be visited by Huygens probe dropped from Cassini

9/30/03Prof. Lynn Cominsky31 Uranus Gas giant, mostly hydrogen atmosphere Gas giant, mostly hydrogen atmosphere Looks blue due to methane in atmosphere Looks blue due to methane in atmosphere Discovered by Herschel in 1781 Discovered by Herschel in 1781 Visited by Voyager 2 in 1986 Visited by Voyager 2 in 1986 Uranus’ pole points toward Sun Uranus’ pole points toward Sun Rock and ice, only 15% hydrogen Rock and ice, only 15% hydrogen No rocky core evident No rocky core evident Clouds and color changes Clouds and color changes 11 known rings 11 known rings Extremely tilted magnetic field Extremely tilted magnetic field 20+ moons, 5 are rather large 20+ moons, 5 are rather large HST image of Uranus and its rings

9/30/03Prof. Lynn Cominsky32 Neptune Discovered in 1846 after being predicted from perturbations in Uranus’ orbit Discovered in 1846 after being predicted from perturbations in Uranus’ orbit Visited by Voyager 2 in 1989 Visited by Voyager 2 in 1989 Composition similar to Uranus Composition similar to Uranus Internal heat source Internal heat source Strong winds and storms Strong winds and storms Great dark spot in 1989, Great dark spot in 1989, not seen by HST in Dark rings seen by Voyager 2 3 Dark rings seen by Voyager 2 Tilted magnetic field Tilted magnetic field 8 known moons, Triton is large 8 known moons, Triton is large HST image of Neptune

9/30/03Prof. Lynn Cominsky33 Pluto Smallest planet and furthest from Sun (usually) Smallest planet and furthest from Sun (usually) Smaller than 7 moons in our solar system Smaller than 7 moons in our solar system Discovered in 1930 by Clyde Tombaugh Discovered in 1930 by Clyde Tombaugh Orbit crosses inside Neptune Orbit crosses inside Neptune No spacecraft observations No spacecraft observations Is Pluto really a planet? Is Pluto really a planet? YES: It has a moon named Charon YES: It has a moon named Charon NO: It resembles asteroids NO: It resembles asteroids NO: It has an elliptical orbit NO: It has an elliptical orbit Rock and ice, little atmosphere Rock and ice, little atmosphere Pluto and Charon

9/30/03Prof. Lynn Cominsky34 Cratering Mercury and the Moon show the results of bombardment during early formation of solar system Mercury and the Moon show the results of bombardment during early formation of solar system Mercury Moon

9/30/03Prof. Lynn Cominsky35 Earth’s Surface Q: Why does the Earth’s surface show little evidence of cratering? 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 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. A: Earth’s surface is actively reforming due to volcanic activity, erosion from water, plate tectonics,etc.

9/30/03Prof. Lynn Cominsky36 Volcanic Activity Io Jupiter’s Moon) shows volcanic activity Io Jupiter’s Moon) shows volcanic activity Venus also has lava flows Venus also has lava flows Prometheus volcano on Io Magellan Radar image of Venus

9/30/03Prof. Lynn Cominsky37 Erosion and Water Erosion (most likely due to liquid water) also seems to have affected Mars, which also has mountains and craters 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 Moon has frozen water at poles but no signs of erosion Mars

9/30/03Prof. Lynn Cominsky38 Where is the Water? Europa (Jupiter’s Moon) Europa (Jupiter’s Moon) thin outer layer of water ice (1-10 km thick) thin outer layer of water ice (1-10 km thick) possible liquid water ocean underneath the surface possible liquid water ocean underneath the surface Callisto (Jupiter’s Moon) Callisto (Jupiter’s Moon) Ice-rock mix throughoutIce-rock mix throughout Possible salt water underneath surface Possible salt water underneath surface

9/30/03Prof. Lynn Cominsky39 Where is the Water? Saturn Saturn Rings are mostly water ice Rings are mostly water ice Will be studied by Cassini in 2004 Will be studied by Cassini in 2004 Titan (Saturn’s Moon) Titan (Saturn’s Moon) Water icebergs in an ocean of methane? Water icebergs in an ocean of methane? No water in atmosphere No water in atmosphere Huygens probe will be dropped from Cassini Huygens probe will be dropped from Cassini

9/30/03Prof. Lynn Cominsky40 Planetary Missions MESSENGER (MErcury Surface, Space ENvironment, GEochemistry and Ranging), being built for launch April 2004, arrives at Mercury in 2009 MESSENGER (MErcury Surface, Space ENvironment, GEochemistry and Ranging), being built for launch April 2004, arrives at Mercury in 2009 Venus program – no current plans 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, 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.

9/30/03Prof. Lynn Cominsky41 Mars – 5 spacecraft on their way! Pathfinder (1996) Pathfinder (1996) Global Surveyor (1999) then two disasters. 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, Two NASA landers (Spirit and Opportunity) are on their way to Mars, due to land on January 4 & 25, Europeans: Mars Express orbiter and Beagle 2 lander – due to arrive 12/26/03 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 Japanese orbiter (launched in 1998) will arrive at Mars in January 2004.

9/30/03Prof. Lynn Cominsky42 Spirit and Opportunity Launch movie Entry movie Exploration movie

9/30/03Prof. Lynn Cominsky43 Europa orbiter – approved then eliminated in FY03 budget. Officially “under study.” Europa orbiter – approved then eliminated in FY03 budget. Officially “under study.” Cassini mission to Saturn arrives July Will drop an ESA probe (Huygens) onto Titan, and flyby Titan and three smaller moons. Cassini mission to Saturn arrives July 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 Pluto/Kuiper Express – Preliminary designs under consideration. Possible launch in 2006, to arrive Planetary Missions

9/30/03Prof. Lynn Cominsky44 What makes a world habitable? In groups of 3-4, take a set of cards that summarize the properties of various solar system bodies In groups of 3-4, take a set of cards that summarize the properties of various solar system bodies Temperature Temperature Water Water Atmosphere Atmosphere Energy Energy Nutrients Nutrients Consider the following: Consider the following: What does life need? What does life need? What kinds of conditions might limit life? What kinds of conditions might limit life? Select your top three candidates for life Select your top three candidates for life

9/30/03Prof. Lynn Cominsky45 Web Resources Nine Planets tour Nine Planets tour Martian Meteorite meteorite.html Martian Meteorite meteorite.html Solar System missions Solar System missions Schrodinger: Schrodinger: