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We have had a long fascination with this:

• HG Welles wrote an interesting story about it
  

• The telescopic appearance of Mars can show "subtle" changes over time. This is due to wind blown dust changing the large scale features and reflective characteristics. In the late 19th century Schaperilli imagined he saw linear features which he called "canals"
  

• Schaperilli's atlas of Martian Canals captivated the imagination of Percival Lowell who greatly popularized the idea of Life on Mars. Lowell imagined a system of canals that the Martians would use to transport water from the Polar Caps to the more arid regions. He constructed an elaborate globe of mars to illustrate this:
  

  Orson Welles 1939 broadcast of Martians invading New Jersey only served to perpetuate the mythology of the Martians. Unfortunately, the media really does have a powerful effect on people.

So what is Mars really Like?

• Whole Mars
• Looking Around
• Looking around some more

The Viking Lander Mission on Mars (1976) sampled the soil and found evidence of a highly chemical reactive soil and environment. There was no unambiguous evidence for biological processes. Worse still was the mass spectrometer measurements which detected no organic molecules down to a concentraction of less than 1 part in 10 million.

So what about the Martian Meteorite?

• Microscopic examination showed morphological peculiarites?
• once you find one you can find many
• Age dating suggests the following sequence
  • The rock itself is 4.6 billion years old (this by itself is highly unusual)
  • The concentration of carbonates is dated to between 3.6 -- 4.0 billion years ago. This suggests that carbonates were despoited inside the rock as liquid water found its way into cracks
  • 16 million years ago, the rock was part of a large cloud of Martian debris that was blasted off the surface by a large impact
  • 13,000 years ago it felt on the Antarctic Ice Sheet
  • 12 Years ago it was found

By analogy with the development of early life on the earth, starting which chemical processes that synthesized organic molecules and rained them into the oceans, we believe that oceans are required for the development of early life:

• Shields sensitive Organic Molecules from UV radiation
• Acts as a transport medium that facilitates interaction

Was there water on Mars?

• Yes, there is now
• There is evidence of flooding
• More evidence
• Agent for Water Production

The ability for liquid water to exist on the Martian surface depends upon the atmospheric pressure. Current atmospheric pressure is 1/1000 that of the earth - way to thin of atmosphere for water to exist.

However, in the early history of Mars there was enough Carbon Dioxide present to form an atmosphere that was 2 times as thick as the present day atmosphere of the Earth (note the early earth's atmosphere was 50 times its present capacity).

At this pressure, water could exist as a liquid on the Surface. The questoin is, how long did these "oceans" exist. On earth we know it took 800 million -- 1 billion years for the first cells to evolve. It is highly unlikely that oceans on Mars existed for that long - it is mostly likely that they only existed for a few 10's of millions of years before the atmospheric pressure lowers to the point that liquid water can longer be sustained

Where does the atmosphere go?

• Freeze out at the Poles
• Gradual escape - Mars is a very small planet; has only 1/2 of the earth's gravity

The most probably explanation of the morphological features seen in the Martian Meteorite is a chemical reaction. Factors that work against the biological interpretation are the following:

• The structures are 10--20 times smaller than similar "micro fossils" seen on the earth. This is a real problem - the structures aren't really big enough to "hold" DNA

• Carbonate concentrations in meteorites can easily be produced by chemical reactions that happen when the rock is shocked. This happens at high temperature (700 C) -->definitely not conducive for biology

• Magnetic fields have played a role in the evolution of bacteria on the earth. They use the magnetic field to sense their position. On Mars there is no magnetic field --> there might have be one in its early history (when the core was molten) but it would have been very weak.

• All of the evidence remains morphological
• Timing of the announcement and general quietness from other meteorite labs regarding the morphological features

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