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Martian Meteorites

Martian Meteorites. Astronomy 315 Professor Lee Carkner Special Lecture. Roys Lecture Tomorrow Night. Dr. Ralph Harvey: “Written In Stone: What the Martian meteorites are trying to tell us about Mars” 7:30 pm, Thursday, May 12, Olin Auditorium

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Martian Meteorites

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  1. Martian Meteorites Astronomy 315 Professor Lee Carkner Special Lecture

  2. Roys Lecture Tomorrow Night • Dr. Ralph Harvey: • “Written In Stone: What the Martian meteorites are trying to tell us about Mars” • 7:30 pm, Thursday, May 12, Olin Auditorium • 5 points extra credit on observing project if you go • See me there to sign in

  3. Rocks in Space • Asteroid -- • Meteoroid -- a small piece of rock in space • Meteor -- • caused by friction • Meteorite -- a meteoroid that hits the ground

  4. Types of Meteorites • Meteorites are classified based on their composition • Iron Meteorites • Iron and some nickel • Stony Meteorites • Silicates (silicon and oxygen) • Contain small round glassy inclusions called chondrules • What are the properties of chondrites and irons and how can you identify them?

  5. Iron Meteorites • Have small depressions on surface caused by heat of passage through atmosphere • These are a particular type of crystal that forms only by very slow cooling (millions of years) • Helps to distinguish true meteorites from terrestrial rocks

  6. Chondrite (Stony) Meteorites • One distinguishing feature is a fusion crust where the outer layers are heated by friction with the atmosphere • Origin uncertain, but indicate that chondrites have never been strongly heated • Carbonaceous chondrites also contain volatiles (water and carbon compounds) and thus represent unprocessed material from the early solar nebula

  7. Selection Effect • Chondrites are the most common type of meteorite • However, chondrites look a lot like normal Earth rocks • Irons are rare • 2/3 of finds are iron • Example of a selection effect • It is an artifact of the way we do our search

  8. Impacts • Most meteoroids are small enough to burn up completely in the atmosphere • Most of the craters are eroded away, only the recent (~100,000 years) one are still visible • In fossil records we see evidence of mass extinction (where most of Earth’s species are wiped out) • Is this due to impacts?

  9. Formation of Meteoroids • Some asteroids became large enough to differentiate • decay of radioactive materials provided the heat • These asteroids were then broken up by collisions • Fragments of the crust form stonys • Asteroids that never differentiated formed chondrites

  10. The Canals of Mars • The red color of Mars led the Greeks and Romans to name it after the god of war • In 1877 G. Schiaparelli thought that he saw intersecting straight lines on Mars • This was translated to English as “canals” implying that somebody built them • Percival Lowell built an observatory near Flagstaff, AZ and published elaborate maps of a network of canals and oasis on Mars • Mars was thought to be very dry, so naturally the inhabitants needed to carefully manage water

  11. Mars Facts • Size: • smallest planet with an atmosphere • Orbit: • most distant terrestrial planet from the Sun • Rotation Period: • almost the same day length as Earth • Mean Temperature: • about -80 F

  12. Spacecraft to Mars • Viking 1 and 2 (1975) extensively imaged Mars and also sent landers to the surface • Current missions: • Mars Odyssey (2001, orbiter) • Pathfinder/Sojourner (1997, rover) • Spirit and Opportunity (2003, rover)

  13. Surface Features • Volcanoes -- Mars has many shield volcanoes, but they are not active today • Canyons -- Mars shows deep canyons, the result of volcanic activity stressing the crust • Craters --The northern hemisphere is less heavily cratered than the southern • Why? • Dust storms alter the Martian craters

  14. The Surface of Mars • Mars is red due to iron oxide (rust) in the soil • Dust storms sometimes cover large fractions of the surface • Mars is cold • Mars has seasons due to the tilt of its axis

  15. Mars’s Atmosphere • Composition: 95% CO2, 3% N2, trace amounts of water vapor and oxygen • About 140 times less pressure than the Earth’s atmosphere • As the water rained out it removed the CO2 • Mars has no plate tectonics to return the CO2 to the atmosphere

  16. Water on Mars • Mars is now a very dry world • A pan of water left out on Mars would boil • Frost is seen on the surface composed of frozen water and CO2 that condensed out of the atmosphere • It is possible that water exists underground

  17. Was Mars Wet? • Surface features indicate that water once flowed freely on the Martian surface • Due to: • Spot flooding (water frozen underground and sometimes comes to the surface)? • Mars may have been warmer with a thicker atmosphere in the past • Where is the water now? • In the polar caps? • Mars may warm up periodically allowing water to form (Mars may now be in an ice age)

  18. Life on Mars? • Mars shows evidence for liquid water and higher temperatures in the past • Could that life have survived? • We do have a few meteors that were blasted off the surface of Mars • AH84001 shows some features that look a little like the remains of life-forms, but evidence is not very strong

  19. Mars forms Mars is cratered Volcanism creates volcanoes and lava flows Mars losses internal heat, crust cools Atmosphere loses CO2, atmosphere cools Lava flows stop A Possible History of Mars

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