Scientists now recognize that life on Earth can dwell in an astonishing number of unusual habitats and under what are considered to be extreme physical conditions. Experts keen on finding life in extreme environments--not only on Earth but elsewhere in our solar system and beyond--met here August 4-7 in a special workshop for journalists.

The meeting was sponsored by the University of Colorado, Boulder's NASA Astrobiology Institute, the Laboratory for Atmospheric and Space Physics, and the Center for Environmental Journalism.

Specific to Mars, the study of thermal spring may help focus the exploration strategy for the red planet.

"It's not just to look at the surface of Mars, but maybe to look at certain places on Mars," said David Des Marais, an astrobiologist at NASA's Ames Research Center at Moffett Field, California. Des Marais is a science team member for the Spirit and Opportunity robots now carrying out extensive and extended field work on Mars. And in a kind of all-things-being equal, knowing Mars may help us to become more acquainted with early Earth, he said.

"Earth is so active. It has been very effective at destroying the first several hundred million years of its earliest record," Des Marais said. "Life could have begun so early in the history of the Earth that any record of that origin has been destroyed."

So if indeed there ever was life on Mars, "we might get closer to understanding origins by studying samples from Mars than from Earth," Des Marais told workshop participants.

Chemical consequences

Des Marais said that this week's liftoff of NASA's Mars Reconnaissance Orbiter (MRO) is important to scoping out habitable cubbyholes on Mars. One of the key attributes of MRO, Des Marais said, is teasing out the mineralology of Mars...to spot "the chemical consequences of hydrothermal activity."

Yet with all the tools orbiting and on the surface of Mars, answering the question of whether life took hold--and may still remain there--is a tough nut to crack.

"I really think this life thing is going to take a while to do...in part, by looking at how long it took us to find evidence of early life on Earth," Des Marais explained. "The surface of Mars is equal to the continental area of the Earth. It's going to take a few iterations."

Given the type of environments on Mars and other celestial locales, can scientists truly expect to play out the whole story by simply digging around here on Earth?

"We definitely can't get the 'whole story' about the potential for life elsewhere by looking here on Earth," said Tom McCollom, a research associate with the Center for Astrobiology and Laboratory for Atmospheric and Space Physics at the University of Colorado, Boulder.

The reasons are twofold, McCollom observed. For one, there are significant differences in the physical/chemical environments on other planetary bodies that the organisms there would have adapted to. Secondly, organisms on other planets would have evolved along pathways so that their biochemistry would likely be significantly different than terrestrial organisms, McCollom said.

"On the other hand, there are enough similarities in the physical/chemical environments on Earth and those that occur elsewhere that we can learn a great deal about what to expect -- and where to look--by examining certain habitats on Earth, like hot springs and the subsurface," McCollom told SPACE.com. "While there will be certain constants from one planetary body to the next, the exact nature of the organisms and the biochemical pathways they use are likely to be quite different."

McCollom said that, because of the lack of oceans on Mars--at least in recent times--hot springs like those in Yellowstone serve as a much better analog for possible habitats on the red planet.