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NMSU astronomer participating in Mars Polar Lander mission

Dust in the wind. That's what Jim Murphy will be focusing on when the Mars Polar Lander arrives in a previously unexplored region of the red planet early next month.

The New Mexico State University astronomy professor, who specializes in Martian meteorology, recently got the green light from NASA to use the Polar Lander's instruments to determine how much dust blows into or out of the polar region during the spacecraft's 90-day mission.

Mundane as that may seem to some of Murphy's fellow New Mexicans, who can measure the seasons by the amount of dust that blows into their homes, the findings could be important to scientists in piecing together the climate history of Mars. And that relates directly to the question of whether Mars in the past may have had enough liquid water to sustain life as we know it.

If all goes well, the Polar Lander will not only provide a close look at a little-known region of Mars, it will also send back -- for the first time -- sounds from the surface of another planet. But that "if" looms larger than usual in the wake of the failure in September of the Mars Climate Orbiter.

"I guess the most interesting question right now about this project is will it succeed, in light of what happened with the orbiter," Murphy said. "A lot of people probably will be watching this one the way they watch a car race to see an accident."

Murphy and other scientists have been scrutinizing the Polar Lander project to maximize the prospects for a successful landing at approximately 12:50 p.m. MST on Dec. 3. He participated recently in a review of the atmospheric modeling that is being used to predict the spacecraft's behavior as it descends to the surface of Mars. The result, he said, was a "slight tweaking of the profile," a change of a few degrees in the temperatures the craft is expected to encounter as it lands in a region of Mars never explored before.

The reviews are part of a wide range of actions taken by NASA following the loss of the Mars Climate Orbiter due to a failure to translate English units into metric units in a segment of the orbiter's navigation-related software. "They are going through everything very carefully, because another failure would be a disaster," Murphy said.

Assuming the Polar Lander project is successful -- as three Mars landers and four Mars orbiters have been since NASA began exploring the planet's surface three decades ago -- it will transmit sounds as well as images. It is the first planetary spacecraft to carry a microphone.

"I expect it will hear the movement of the lander's mechanical arm," Murphy said. "It will hear the wind blowing."

The lander's primary mission, however, is to study the uniquely layered terrain near the planet's southern polar cap, which will give scientists important information about the climate history of Mars. Determining how much water is in the region's layers of dust and ice, for instance, will help determine how much water might have existed on the planet in the past, "and all of this goes back to the issue of life on Mars," Murphy said.

As it happens, the spacecraft will land on Mars during a season roughly equivalent to Earth's. "It will be the seasonal equivalent of early December on Mars, heading toward the solstice," which in the southern hemisphere will be the summer solstice, Murphy said. That means the sun will be up all day in the southern polar region, which is significant because the lander uses solar power.

Originally, the Mars Climate Orbiter and the Mars Polar Lander were designed to work as a team, with the orbiter studying the planet's current climate, the lander digging into clues about the past, and the orbiter relaying communications from the lander to Earth. With the loss of the orbiter, most of the lander's communications will be direct to Earth, although it may be able to use the still-orbiting Mars Global Surveyor spacecraft for some communications, Murphy said.

As a result, the lander won't be able to collect as much on a daily basis, because it will be spending more time and energy transmitting data, he said.

The lander probably will encounter temperatures ranging from highs of about minus 10 to minus 15 degrees Celsius, or around 5 to 15 degrees Fahrenheit, to lows of about 40-below on either scale, Murphy said. The terrain will be much different from the rocky surface seen by previous missions.

"Both polar regions on Mars have a layered geology, sort of like stair steps," he said. "It's believed that this has some relationship to climate changes. This is material, ice and dust, that has been deposited from the atmosphere over time." Most of the ice probably is composed of water, Murphy said, with some carbon dioxide ice also probably present. Carbon dioxide is the primary gas in Mars' atmosphere.

Knowing how much dust blows into or out of the region during the 90-day mission, and whether the dust is mixed deep into the Martian atmosphere or concentrated near the surface, will be valuable in a number of ways, Murphy said.

"We can run our computer models for the season in which the lander will be active and compare that to what we actually measure," he said. "If you have a model that agrees with your actual observations, then you can be more confident in using your model to extrapolate over long periods of time. If the model doesn't agree, you figure out what the discrepancy is and in that way you improve the models that we use."

As a participating scientist, Murphy will work with the project's meteorology team in deciding how to collect, process and analyze data. He also will be involved in archiving the data that the lander sends back, for use by scientists the world over. The Planetary Atmospheres Node of NASA's Planetary Data System is headquartered within the astronomy department at NMSU, under the direction of NMSU astronomer Reta Beebe.