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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
Martian Meteorites

Astronomy 315

Professor Lee Carkner

Special Lecture

roys lecture tomorrow night
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
rocks in space
Rocks in Space
  • Asteroid --
  • Meteoroid -- a small piece of rock in space
  • Meteor --
    • caused by friction
  • Meteorite -- a meteoroid that hits the ground
types of meteorites
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?
iron meteorites
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
chondrite stony meteorites
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
selection effect
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
impacts
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?
formation of meteoroids
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
the canals of mars
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
mars facts
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
spacecraft to mars
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)
surface features
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
the surface of mars
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
mars s atmosphere
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
water on mars
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
was mars wet
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)
life on mars
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
a possible history of mars
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