Polycyclic Aromatic Hydrocarbons
Large, complex organic molecules which were found near the carbonate globules
(which lined the fissure in ALH84001) and are consistent with the breakdown
products of living organisms. These are the first organic molecules associated
with Mars (recall Viking found no traces of organic compounds in the soil of
Mars -- at its two sites).
Contaminants?
- Rate of PAHs laid down on Greenland (based on ice cores) would lead to
concentrations 1,000 to 1,000,000 times lower
- Analysis of a heavily weathered Antarctic meteorite did not
show the presence of
Terrestrial PAHs
- Analysis of the interiors of two ordinary chondritic Antarctic meteorites
showed no interior PAHs
- Studies of the
outer layers of the ALH84001 meteorite
revealed that the
PAHs were interior to the fusion crust ===> did not seep in
Seems that they made a reasonable case that the PAHS were indigenous to
ALH84001.
Biology?
- PAHs are fairly common. They are found in other
meteorites, interplanetary dust,
and interstellar dust--the residue of nonbiological activity. the spectrum of
the PAHs is much less diverse than found in Terrestrial biological material.
- Maybe weathering is more complex than their tests allowed
Biology is not so clear
