Thomas Gold, Emeritus professor of Astronomy at Cornell University, outlined his views about Martian life at a February conference. He believes life probably evolved on Mars, and still exists. Since he believes life on Earth has existed in this habitat for billions of years, he says a similar situation is likely for Mars and other rocky planets. Gold proposed the theory in 1992, and was first to suggest checking the Martian meteorites for microbes. He claims meteorite ALH84001 supports his theory, since it apparently contains solid residues of biological activity.
Gold says the key to the theory is helium's association with Earthly petroleum deposits.
Radioactive decay of uranium and thorium generates diffuse helium, but no biological process can concentrate it to the levels found in petroleum. He says petroleum originates at great depth, not from surface biological sediments, collecting and concentrating helium as it moves through rock. If so, helium must have risen from depths of at least 160 km, not just the top 6 km where biological sediments exist. Subterranean microbes have since been confirmed. Gold said that if hydrocarbons are created deep within Earth, and geologic forces raise them to where microbes feed on them, then it's a small step to suppose similar processes exist on similar bodies in the solar system.