QUESTION:
When there was life on Mars, what were some similarities between them and 
life on Earth?									

ANSWER from Jack Farmer on February 11, 1997:
We are not certain that life ever developed on Mars. That is 
something we hope to find out during the missions we have planned.  It 
may take us a long time to determine if life ever developed on Mars, but
at least we now have a strategy for exploration, which we hope to implement
over the next 10 years or so.  In terms of what we expect to find, we think
if life ever developed on Mars it is likely to have been microscopic.  We
also favor the idea that Martian life could have lived under environmental
extremes similar to many of the microorganisms on Earth, adapting to such
conditions as very high salt, very high temperature, or very cold
temperatures near freezing.  Microbes thrive in such extreme environments
on Earth.  We also think there is a reasonable chance that if life
developed on Mars, it may still be present  in the deep subsurface where
liquid water is stable.  This groundwater environment has probably offered
the most important and long-lasting environment on Mars since its origin.
Liquid water is regarded as an essential ingredient for life, and in
looking for life, we essentially are looking for either past or present
water. - Jack Farmer

Jack D. Farmer, PhD.
NASA Ames Research Center