Springtime at Mars' southern polar cap

Mars has seasons, just as Earth does. Using the Mars orbiter camera on Surveyor, scientists are now able to monitor the red planet's weather changes from one martian year (about twice as long as an Earth year) to the next. One of their discoveries has been that the southern polar ice cap, long thought to be permanent, isn't so permanent.

"What we're finding is just short of incredible," said Edgett. "For most of the Mars year, the weather patterns are very predictable. Last year, in late June, we had global dust storms that obscured the planet for three months - an event that did not fit the patterns we'd otherwise seen. We found that there were lots of storms going on at once, not that there was one gigantic global dust storm, as was thought during previous events."

Thorpe said, "The weather reports are very important, since weather will affect future spacecraft landings and operations on the surface of Mars, including the 2003 Mars Exploration Rovers."

Weekly Mars weather reports are available by going to the Mars Exploration page at http://marsprogram.jpl.nasa.gov and clicking on the How's the Weather on Mars box.

Students interested in exploring Mars further can go to http://marsprogram.jpl.nasa.gov/classroom/students.html for more information on the red planet.

Extensions Lead to Discoveries "One of the reasons I'm so very excited about the second extension is because every week there is something new and surprising in our data," said Mars scientist Ken Edgett. "And what's really cool is that every four to six months we discover something totally amazing. Last year, we were flabbergasted to find that the southern polar "permanent" ice cap isn't so permanent. We're now tracking changes to the cap on shorter time scales." Each winter, frost forms a seasonal polar cap covering everything from 60 degrees latitude to 90 degrees latitude; it retreats in spring. The permanent ice cap, which is mostly carbon dioxide, remains through the entire summer and was previously thought to be permanent. "We now know that even in summer the ice is subliming (converting directly from solid to vapor) at a rate that suggests the entire cap could disappear in a few thousand to tens of thousands of years," said Edgett. "There's a lot of carbon dioxide in the permanent cap, but we're finding that it is going away on a larger time scale [than the seasonal frost], independent of season." For more information and images, please see http://www.msss.com/mars_images/moc/CO2_Science_rel/ .