JACKSON HOLE, Wyoming -- There is mounting evidence of the role of water in Mars' evolution. That fact appears to have been favorable to the development of life -- and the leftover calling card of past biology may be preserved in that world's geologic record.

Scientists from around the world have gathered here to present what is known, as well as agree on need-to-know essentials, at The Second Conference on Early Mars: Geologic, Hydrologic, and Climate Evolution and the Implications for Life.

Even more compelling is the thought that life may well have taken a beating and kept on ticking over time. And if so, where on the planet is it today? Scientists are admittedly awash in new data.

Mars is being scrutinized daily by the largest contingent of sensor-laden orbiters and rovers ever sent there. But teasing out the planet's secrets is a daunting, long-term task. A crossbreeding of research talents to investigate Mars has proven essential.

Dangerous business

"Mars is a hellishly complicated and enormously large planet," noted Steve Squyres of Cornell University and leader of the science teams for the Mars Exploration Rovers (MER) -- Spirit and Opportunity -- that remain alive, well, and hard at work.

Mars has a total land surface area the same as the total land area of the Earth, Squyres said. No surface mission is going to address the global truths about Mars.

"Our mission is fundamentally addressing issues of ancient water and habitability at two specific sites. And extrapolating those broadly and globally is dangerous business," Squyres told SPACE.com .

The influx of new data received from the MER rovers has been striking.

Yet the richness, the diversity, and the complexity of the two landing sites -- Gusev Crater and Meridiani Planum -- outstrips what you could do if there were 10 MER machines at each site, each operating for a decade, Squyres advised.

"The thing about a rover mission is that, as long as you can keep moving, there's always something new over the horizon," Squyres related. "A rover's work is never done."

Eureka moments

The twin land rovers, the European Mars Express, as well as NASA's Mars Global Surveyor and Mars Odyssey orbiters - all these spacecraft are making contributions to grasp the nature of the martian surface.

"But like it is in any particular discipline, as you learn more you ask more questions," said Steve Clifford, lead organizer of the conference from the Lunar and Planetary Institute in Houston, Texas. "You begin to realize the things you thought you had a good handle on...well, maybe you don't."

For instance, the history of water on Mars, its state and distribution and the role of water in the evolution of the planet today - there's a revolution underway in our understanding of this issue and others, Clifford said. Furthermore, is water lurking subsurface at Mars and how might that boost the prospect for life today?

Clifford said the first Early Mars meeting was held in 1997, spurred by the revelations over the so-called "Mars rock" - the ALH84001 meteorite -- and claims that it possibly carried evidence for martian microbial life.

Now jump ahead some seven years later. "There are a lot of pieces to the puzzle," Clifford explained, regarding the environment that might have existed very early in martian geologic history.

"It's very likely if there was a biosphere on Mars, there's a signature of that biosphere preserved in the ice that might be present in the northern plains of the planet," Clifford said. Major questions in his mind: Where the water went? And where a biosphere that could have evolved on Mars might go in order to survive to the present day?

"The key is an interdisciplinary approach. If you just have one particular discipline, you don't develop the synergies. You don't develop eureka moments," Clifford said.

Water: pervasive and long-lived?

Mars researchers are in "a real struggle" trying to put everything into context, said Laurie Leshin, a planetary scientist at Arizona State University in Tempe, Arizona. "Think about trying to understand the Earth by landing on a bicycle in Alabama and Australia. We have to keep in mind that Mars is a complex, enormous planet."

Leshin said there is no concrete evidence that there ever was life on Mars. But that possibility has been bolstered by the realization that there's an incredible diversity and distribution of life on Earth, she said.

"I'm more optimistic this year than I was last year," Leshin said about the life on Mars issue and environments on the planet conducive to life. "But it's tricky still."

"I'm still not at that early Mars was warm and wet conclusion," Leshin added.

Nevertheless, the two ancient terrains visited by Spirit and Opportunity and two hits on some kind of water, "that's good," Leshin said.  "Whether it was pervasive and long-lived and all over the place and oceanic, who knows...we just don't know."

Boot marks on Mars

Thanks to the onslaught of data streaming in from on-duty Mars spacecraft, the outlook that the red planet was once a habitat for life is far higher today than in the past.

That's the notion of Dave Des Marais, a Mars Exploration Rover long-term planning leader from NASA's Ames Research Center, located near San Francisco, California. The question used to be: "Is there any place we can go on Mars' surface and find evidence of liquid water?" Today, the inquiry is: "Given the places on the surface where there was liquid water, what's the best place to go to increase our chances of seeing, potentially, evidence of life?"

"So I think we've notched the whole thing up," Des Marais told SPACE.com . "We know liquid water was there and was there a long time. Amongst all these places where water has expressed itself, which is the best one that allows us to take that next step...toward discovering evidence of life?"

Des Marais said robotic explorers are setting the stage for follow-up human expeditions to the red planet.

Prior to humans putting their boot marks on Mars, a milestone still ahead is robotic return to Earth of martian samples. "The first return sample has to be more than a handful of loose dust. I'm definitely more upbeat about getting really great stuff in the first sample return today than a year ago," Des Marais stated.

"The human mission to Mars is going to be such a huge investment. When it goes, I just want it to be a smashing success. What we do in the robotic phase of Mars exploration will really set us up for a smashing success when humans go there," Des Marais concluded.