Probe Aiming to Land on Mars Ice

Aug. 3, 2007 — For the past decade, NASA's plan for exploring Mars has been to follow the trail of water. On Saturday, the agency plans to launch a robotic probe that will land right on it.

The spacecraft, called Phoenix, will be the first to explore the frozen polar region of Mars, an area that is believed to hold vast reservoirs of water ice.

"Water and life go together," said Ray Arvidson, with Washington University in St. Louis and one of the lead scientists on the Phoenix mission. "We want to confirm that water ice is just below the surface."

Scientists have many questions about Mars' water. Previous spacecraft, including the twin rovers Spirit and Opportunity, turned up ample geologic and chemical signs that water once existed on what is now a cold and dry desert. But no one knows what happened to it, nor if it was in a liquid state long enough for life to evolve.

Phoenix will not directly look for life on Mars. Instead the probe will use a 7.7-foot-long robotic arm to drill down into the frozen ground and retrieve ice samples to determine if Mars was chemically suited to support life.

"The greatest result we can find is that there is a wealth of complex organics associated with that ice. That would give us the sense this is the place to go search for life on Mars," said Phoenix lead investigator Peter Smith, with the University of Arizona.

Mars rovers celebrate a big milestone.

Unlike NASA's intrepid rovers, which are still waiting out dust storms before they can continue with their investigations, Phoenix will remain stationary at its landing site. The journey to Mars, which is scheduled to begin with launch aboard an unmanned Delta rocket at 5:26 a.m. ET on Saturday, will take nine months.

Engineers have taken great pains to avoid the fate of some of Phoenix's predecessors, including Mars Polar Lander, which carried some of the same instruments now aboard the new probe.

Polar Lander was the second of two Mars probes lost in late 1999 as they attempted to settle on or around the planet. NASA canceled a lander mission that was to have been part of the 2001 Mars Surveyor mission in the wake of the accidents.

As its name implies, Phoenix, a mythical bird that reforms from its ashes, is a resurrection of that craft as well.

"We have tested and tested again to make sure we pulled out all the risk we could," spacecraft program manager Ed Sedivy, with manufacturer Lockheed Martin Space Systems, said a a news conference on Thursday.