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Announcements

Announcements. Passing out marks-so-far today with assignments ½ of available marks now given out Can always do `bonus assignments' (worth 2 credits) Find current news article relevent to the course (1 credit) Briefly describe it and its relevence to the course (1 credit). The Search: Mars.

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Announcements

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  1. Announcements • Passing out marks-so-far today with assignments • ½ of available marks now given out • Can always do `bonus assignments' (worth 2 credits) • Find current news article relevent to the course (1 credit) • Briefly describe it and its relevence to the course (1 credit)

  2. The Search: Mars • A Short Biography of Mars • The Planet and its History • The History of Mars Exploration • Past • Current • Future? • The Search for (past) Life on Mars • Viking Experiments • Microbial Fossils

  3. A Portrait of Mars as a Small Planet • Mars • The atmosphere of Mars • How it came to be that way

  4. Mars • Red planet between Earth and Asteroid Belt • Half again as far away from Sun as the Earth is • Expect it to be ~100o F colder than Earth on average • Average too cool for water • Peak temps ~ 70o F (but -130 at night!)

  5. Mars • Near asteroid belt • Likely more collisions than Earth • Large impacts can blow off significant rocky material • Meteorites • As well as gases (atmosphere)

  6. Mars • ~1/2 radius of Earth • ~1/10 mass • ~40% surface gravity • Force of a 1 lb weight less than ½ lb on Mars • Less gravity holding the atmosphere in place

  7. Mars • Too little gravity to be able to hold onto a significant atmosphere • Atmospheric pressure less than 1% of Earth's

  8. Evaporation • What causes evaporation of liquid, and what prevents it?

  9. Evaporation • What causes evaporation of liquid, and what prevents it? • Fastest moving water (say) molecules can escape into atmosphere • Water molecules in atmosphere can collide into water and become part of the liquid • Balance is reached when evaporating water = condensing water

  10. Evaporation • Can change balance: • Little water in atmosphere, evaporation happens faster • (Why feel so sticky on a humid day) • If air pressure is very low, evaporated water molecules can move very far away from pool of water • Fewer around to condense • Faster evaporation

  11. Evaporation • Effect of atmospheric pressure happens on our own planet • Reason for `high-altitude cooking instructions' on some boxes • Higher altitude -> lower air pressure -> evaporation is easier -> lower boiling point

  12. Evaporation • Martian atmospheric pressure < 1% of Earth's • (Earth's atmosphere at 15 miles / 80,000 ft) • Water boiling point is so low that any liquid water evaporates immediately • No free water possible on surface

  13. Evaporation • But water ice DOES exist on Mars: • Polar ice caps • Mostly (on top) dry ice (frozen CO2) • Underneath, visible when CO2 has sublimated, water ice • Quite likely some trapped under surface: `permafrost'

  14. Atmospheric Pressure • Atmospheric pressure is seasonal • Dry ice caps melt • Increase CO2 in atmosphere • Increase atmosphere pressure • Dry ice caps re-freeze • Pressure decreases

  15. The Reasons for the Seasons • Earth's (and Mars') axis is tilted • Earth: 23.5o (Mars: 25.9o) • Tilt stays in same direction as planet orbits Sun

  16. The Reasons for the Seasons Summer • Sun comes in at different angle when planet is at different positions • Summer: • Light most direct • Sun closest to being overhead • Winter • Comes in at angle: • Same amount of light covers larger area • Increased reflection Winter

  17. The Reasons for the Seasons Fall: Cubs win (effective 2003) • Orientation changes over course of year • Another effect: Earth is slightly further from Sun in (Northern Hemisphere) Winter than in Summer • Only ~1% effect (5oF) • Effect of orientation ~16% effect (90oF) Winter: Bears Lose Spring: Bulls Lose

  18. Ecliptic • Because of Earth's tilt, equator (and rotation) do not line up with plane of the solar system • Solar system objects (Sun, Moon, planets) apear to lie along an arc – ecliptic

  19. Ecliptic • Planets are along plane of solar system • Appear on Earth to along an arc • Mars visible these days early at night towards the East, even from Chicago • Bright reddish `star' • Near a bright greenish-yellow `star' (Venus) Starmap for tonight, 9pm

  20. How Mars Came to Be This Way Large Enough for Atmosphere • Distance from Sun makes global liquid water difficult but not impossible • NO ATMOSPHERE • Liquid water quickly evaporates • No greenhouse effect to warm planet, regulate temp. • No ozone to protect from UV Not Large Enough for Atmosphere

  21. The History of Martian Exploration • Past explorations • Current Rover Missions • Future Plans

  22. Exploration of Mars Today • So many recent missions to Mars that it's becoming almost anticlimatic • News filled with discoveries from current rovers • Still very difficult: • Success rate low! • Scientists can't go there at whim yet

  23. Observations of Mars from Earth • Early telescope observations: • `observations' of canals • Improved telescopes showed this not to be the case • Later, radio observations • Surface temperature • Crude radar maps of surface

  24. 1960-2: Korabl (`Marsnik') • Attempted Russian Probes • 4 attempted flybys, 1 attempted landing • Most barely made it past Earth orbit, one was lost between Earth and Mars

  25. 1964: Mariner, Zond • Mariner 3, 4 (USA): attempted flyby • Mariner 3: Couldn't make it to Mars • Mariner 4: First flyby, close up pictures • Zond 2 (USSR): Russian flyby, descent • Lost on its way to Mars

  26. 1969: Mariner, Mars 1969 • Mariner 6,7: Identical flyby craft • Mariner 4: First flyby, close up pictures • Mars 1969A/B: Russian flyby, descent • Didn't survive takeoff

  27. 1971: Mariner, Mars 2/3: Orbiters • Mars 2/3 (USSR): First orbiter of another world • Measured temps, magnetic fields • Sent probe, 1 crashed too fast, other survived 20 hours Mariner 8 didn't make it • Mariner 9: Orbited, obscured by storms • First close-up views of moons of Mars

  28. 1973: Mars 4/5/6/7 (USSR) • Mars 4: Brakes didn't work; flew by instead of orbited • Mars 5: Successful Orbit, pictures • Mars 6: Descent, sent data from atmosphere before shutting down, but data garbled • Mars 7: Missed Mars entirely

  29. 1975: Viking 1,2 (USA) • Identical Orbiter + lander • Orbiters searched for safe landing places • Extensive weather measurements, chemistry/biology experiments • Sent several thousand images, data

  30. 1988: Phobos 1,2 (USSR) • Lost due to human error (Phobos 1), computer malfunction (Phobos 2)

  31. 1988-1992 • 1988: Phobos 1, 2 (USSR) • Lost due to human error (Phobos 1), computer malfunction (Phobos 2) • 1992: Mars Observer (USA) • All contact lost 3 days from Mars

  32. Very Recent Mars Missions • 1996: • Mars 96 (USSR): Didn't successfully leave Earth • Mars Global Surveyor (USA) • Looking for places to send Pathfinder • Still sending back data • Mars Pathfinder • Probe with some sensors • Test of new technologies, techniques

  33. 1998: Less Successful • Nozomi (Japan) • Navigation problems • Could not reach Mars at expected time • Unable to orbit Mars • Mars Climate Orbiter (USA) • Crashed into Mars after mistake in converting units in probe computer programming

  34. 1998-9: Less Successful • Nozomi (Japan) • Navigation problems • Could not reach Mars at expected time • Unable to orbit Mars • Mars Climate Orbiter (USA) • Crashed into Mars after mistake in converting units in probe computer programming • Mars Polar Lander (USA) • Signal lost near Mars: Navigation errors?

  35. 2001: Mars Odyssey(NASA) • Orbiter • Build global map of telements, minerals on the Mars surface • Determine the abundance of hydrogen in subsurface. -> hidden deposits of water ice? • Structure of the Martian surface. • Radiation environment between the Earth and Mars and in low Mars orbit (radiation-related risk to human exploration) • Communication relay Spirit/Opportunity/Beagle

  36. 2001: Mars Express(Europe) • Orbiter + Lander/Rover (Beagle) • Beagle lost • Image globe in 3D • Build accurate picture of meteorology/climage • Communications Relay

  37. 2003: Spirit, Opportunity(USA) • Search for/study many types of rocks and soils that might hold clues to past water activity. • Maps showing the locations of different kinds of rocks and soils around the landing sites. • What forces have shaped the landscape • Search for minerals that contain water/formed in water. • Identify minerals, how made • Clues to what environment was like in past

  38. The Search for Life on Mars • Pictures of surface • Viking biology experiments • Meteoritic `fossils' • Future?

  39. Venus • Closest to Earth • ¾ as far away from Sun as Earth is • Very similar to Earth's size, density • Covered by thick, opaque clouds

  40. Reading for Next Class (Apr 16) • Chapter 15: The Outer Solar Systen • History of Outer Solar System Exploration • The Nature of Gas Giants • Atmosphere • Chemistry • The Moons of Jupiter, Saturn, Uranus, Neptune • Chapter 16: How Unique is Earth? • Necessary Resources • On Having a Large Moon • Staying alive by accident

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