Mars Photos Appear to Show Dry Hot Springs

Michael Meyer, NASA's chief scientist for Mars, said the findings are intriguing but remain preliminary.

"The discovery of a hot springs would be a very significant one, but making that determination is very difficult based only on data from orbit," he said. "It's very interesting to the Mars community, but it will be open to interpretation."

In late 2006, for instance, a comparison of photographs taken several years apart by another spacecraft, NASA's Mars Global Surveyor, showed that two gullies had appeared on the slope of a crater, suggesting that water might have flowed there in the interval. The report caused great excitement, but scientists have since moved toward the view that the gullies were formed by a slide of loose, dry material, not by flowing water.

Meyer said that the findings of that report were clearly "not a slam-dunk" but that the likelihood remains that there is some liquid water beneath the planet's surface.

Such water would be substantially cooler than in Earth's hot springs, since Mars is colder, and its thinner atmosphere allows water to boil at about 50 degrees Fahrenheit, as opposed to 212 degrees on Earth. That means Martian water would not get any hotter than roughly room temperature, which certainly could support life.

NASA is planning to send a manned mission to Mars sometime after 2030, but in the interim the agency plans to study the planet further with increasingly sophisticated cameras, rovers and a mission to gather Martian samples and bring them back to Earth.

Next month, the Phoenix Mars Lander, a robotic laboratory, is scheduled to land on the largest concentration of Martian ice outside of the polar regions. It is designed to dig into the ice and sample it for microbial life as well as for signs of climate changes. And NASA's two earlier rovers, Spirit and Opportunity, continue to explore the planet almost 4 1/2 years after they landed.

Working with European partners, NASA is planning a mission within a decade to collect rock and dirt samples and return them to Earth. The project has run into budget problems, however, as well as concerns over the risks of bringing back Martian rocks that could contain organisms.

Oehler and Allen said they hope future missions will consider exploring the suspected hot springs -- which are ideal not only for encouraging life but also for fossilizing remains.

"We know from Earth that life might have started in hydrothermal environments like hot springs, and has lasted and been preserved in them," Oehler said. "It could also be true on Mars."