But considered collectively, the circumstantial evidence suggested the presence of "primitive life on early Mars."

Scientists speculate that features in Xanthe Terra show evidence of precipitation on early Mars.

They were hyperthermophiles, so the early Mars of the heavy bombardment suited them just fine.

It is considered an alien environment much like what existed on early Mars.

Dr. Gibson said he believed that there was life on early Mars and that it could still be there.

And last week scientists, deciphering the rock's sensational clues, concluded this was compelling evidence for primitive life on early Mars.

Scientists who believed the picture of a wet, possibly life-filled early Mars needed to explain where the water had gone.

Proof that a vast amount of liquid water existed on early Mars would raise hopes not only that life evolved there but also that it could survive today.

Therefore, the presence of olivine suggests that prolonged water erosion did not occur globally on early Mars.

If life emerged and evolved on early Mars then it is possible, and indeed likely, that physical or chemical biosignatures are preserved in the exposed rock record.