Phoenix probe sheds new light on Mars weather

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(Agencies)
Updated: 2008-12-16 16:32

CAPE CANAVERAL, Florida – NASA is still unable to say for sure whether its Phoenix lander has found a place where life could have existed on Mars.

But scientists working with the US space agency said on Monday computer models they have been using to predict what the weather would be like on the Red Planet are wrong, and more accurate models would give a better picture of its past.

Speaking at the opening day of the American Geophysical Union conference in San Francisco, Phoenix mission scientists laid out the early harvest from five months of robotic operations on the northern polar region of Mars.

In addition to analyzing ice and soil samples for organic material, a process that is still under way, the Phoenix science team collected daily weather reports, information considered critical to learning if the planet could have supported water long enough for life to evolve.

"It's a very active weather environment," lead investigator Peter Smith told reporters in a teleconference. "It's a bit of a mystery how this is happening."

Phoenix saw dusty summer days slip into cloudy fall, replete with ground fog, snow and frost.

"Global climate models that are running on Mars would not predict this," Smith said. "What we're learning now about the polar region is going to force us to make changes."

More accurate computer models would give scientists a clearer picture of what happened in Mars' past, particularly when the planet's axial tilt, or obliquity, was greater than it is now.

Without a large moon for stabilization, Mars' polar regions periodically shift off axis by more than 35 degrees. During those times, the sun would rise higher in the sky above the Martian poles, making for warmer summers.

Scientists are trying to determine if there was ever a period of time when it would have been warm enough for water, considered a key ingredient for life as we know it.

"We're really trying to understand if this was ever a wetter environment," Smith said.

"If we can update these global circulation models and we can understand better about the polar weather, then we can look back in time to see if liquid water was ever a dominant influence on this soil in this location."

The Phoenix team also is on the hunt for evidence of minerals affected by water. Scientists had problems delivering soil samples into Phoenix's tiny ovens for analysis because the soil turned out to be rather clumpy, not dry and dusty like the soil at sites where other probes have landed. Though frustrating, the discovery also spurred new questions about how water is moving through the ice, soil and atmosphere.

"Something is taking the wind-blown material and mildly cementing it," said Ray Arvidson, of Washington University in St. Louis, who served as the lead scientist for the lander's robotic arm.

More results from the Phoenix mission are expected next year.