Martian Asteroids
and the Evidence for Life on Mars

There has long been a fascination about life on Mars
• Lowells "charting of canals on Earth and conviction that a civilization resides there
• Science Fiction writers have written vociferously about life on Mars
  • Edgar Rice Burroughs
  • War of the Worlds - H.G. Wells

The Martian Asteroids:

• About a dozen meteorites from the surface of Mars have been found on Earth
  • (identified by gases trapped in rocks)
• 1984 - scientists discoverd a rock ( ALH84001) on Antarctic ice field
  • 4.2 pounds (about the size of an Idaho patato)
• ALH84001 stored in cabinet for 8 years
• 1992 - detailed study of the rock - found (within a small region of the rock)
  1. organic molecules that might be associated with life
     • iron sulfide and magnetite
  2. several minerals characteristic of biological activity
     • carbonate globules
  3. tiny tubular and egg-shaped structures resembling ancient single-celled bacteria found on Earth
• These observations were announced August 7, 1996

• The history of ALH84001
  • Age of rock: 4.5 billion years (oldest known rock)
  • about 16,000,000 years ago meteorite struck Mars, ejecting this rock into space
    • this time is determined from the exposure to radioactive nuclei in space
  • 13,000 years ago, rock landed on Antarctic ice field
  • 1984 - meteorite specialist drives up in snowmobile and finds the rock
  • about ten years later
    • geoligist identifies ALH84001 as coming from Mars
    • and other scientists suggest it shows evidence of ancient life

• Evidence for life on Mars has not been accepted as FACT
  • This evidence could all have been produced by chemical reactions without any kind of life
  • Could ALH84001 have been contaminated? (it sat on ice in Antarctica for 13,000 years
  • More evidence is need to resolve this
• Some scientists have suggested that "if any rock is examined as closely as ALH84001 has been, unusual properties will be found."

• Obvious related question:
  • Did life emerge on Earth, or
  • did it come from outer space (perhaps from Mars?)
• Many organic molecules are brought to Earth by comets, asteroids, meteorites
  • Why not life itself?
• Every year
  • tons of Martian material falls on Earth
  • and material from Earth also falls on Mars
• It takes an average of about 10 million years to make the journey

• Future NASA visits to Mars will attempt to understand whether life did or did not exist on Mars in the past

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