Hopes of finding evidence that organic life gained a toe-hold on Mars appear to be brightening.
To be sure, no one yet has uncovered direct evidence for life there. An experiment designed to look for it, the European Space Agency's Beagle 2 lander, failed on arrival at Mars in December 2003.
But results from US and European orbiters circling the Red Planet and the discovery of another new species of ice-happy microbes on Earth leave many researchers convinced that it is just a matter of time - and money - before they come up with the "smoking guns."
On Friday, the European Space Agency wrapped up a week-long meeting in Noordwijk, Netherlands, focusing on the first year's results from its Mars Express orbiter. Planetary scientists reported evidence for volcanic eruptions within the planet's recent past. Others have spotted what they interpret as a large, dust- covered frozen sea. Still others cite the presence of methane and formaldehyde in the Martian atmosphere as evidence for current biological activity.
"Hints of life on Mars are getting stronger," notes Vittorio Formisano, whose research group detected the two compounds in the planet's tenuous atmosphere using instruments on Mars Express.
Indeed, an informal survey of participants at the meeting indicated that 75 percent of the researchers present agreed that bacteria once lived on Mars. Roughly 25 percent agreed that bacteria inhabit the planet today.
Meanwhile, a meeting in Houston scheduled for next month will highlight a range of results from Mars Express and from the US Mars Global Surveyor and Mars Odyssey orbiters for near-surface ice and glacial activity in Mars' recent past.
Results pointing to likely ice floes on a frozen sea and to other near-surface ice deposits are "tremendously exciting," says Richard Hoover, an astrobiologist at the National Aeronautics and Space Administration's Marshall Space Flight Center in Huntsville, Ala. If there's life on Mars today, a frozen sea "would be the ideal place to look for it."
The evidence for a frozen sea near Mars' equator comes from Mars Express images analyzed by a team led by John Murray, a researcher at the Open University in Milton Keynes, England. Placed side by side with a picture of Antarctic pack ice, the Mars image looks different only in its signature rust-colored dust.