PSR Discoveries

Alternative Views: Nonbiological Hydrocarbons

Phobos CM chondrites are probably quite common in the asteroid belt, not far from Mars, and so would have rained down on the planet early in its history, depositing organic chemicals that could be buried, dissolved in ground water, and incorporated into rocks, including the one that ended up as the ALH 84001 meteorite. Jeffrey Bell of the University of Hawai'i has noted that Phobos and Deimos, the small moons of Mars, have optical properties like those of CM chondrites. He suggests that these moons are fragments of a larger original moon that was busted apart by either impact or tidal forces. The fragments would have fallen to Mars, depositing vast amounts of nonbiological hydrocarbons. (NASA photo.)
Elliptical craters on Mars Peter Schultz (Brown University) has drawn attention to the high abundance of non-circular craters on Mars, such as the one shown here next to a volcano called Ceranius Tholus. He suggests that these elliptical craters were formed by oblique impacts. A logical way to produce the exceptional number of low-angle impacts observed on Mars is for the impactors to be in orbit around the planet. This supports Jeff Bell's proposal that Phobos and Deimos, and their precursor moon or moons, provided the needed carbonaceous material to produce PAHs. Of course, merely having a ready source of hydrocarbons does not rule out the interpretation that the PAHs in ALH 84001 were produced by biological processes. In fact, the presence of abundant hydrocarbons on the surface of Mars would provide the raw materials from which life could have arisen. (25oN, 97oW, NASA photo.)
RETURN to Life on Mars Update in the March 1997 issue of PSRD.