Risky landing on Red Planet

Spacecraft to reach Mars, begin search for water and life

May 24, 2008|By Dennis O'Brien | Dennis O'Brien,Sun reporter

When it lands tomorrow, NASA's Phoenix spacecraft will begin three months of digging in the Martian soil, looking for clues that might tell whether the Red Planet has ever seen oceans, rivers or even microbial life.

But first, Phoenix will have to survive a nerve-racking seven-minute descent that begins with a 12,000-mph plunge through the Martian atmosphere and ends with a three-point landing that will require 26 separate mechanical steps, including release of a parachute, jettisoning of a heat shield and the firing of thrusters to slow down the craft.

"There's a lot that has to go right in a very short period of time," said Barry Goldstein, NASA's Phoenix project manager.

A key factor for a safe landing is the accuracy of advance imaging work conducted by scientists at the Johns Hopkins Applied Physics Laboratory near Laurel, who helped pick a landing site free of rocks that could damage the spacecraft.

Astronomers say the potential payoff is worth the $420 million cost of the mission.

"It could add a lot to what we know, complementing what NASA has going on with Mars. The possibilities are really fascinating," said James F. Bell III, an astronomer from Cornell who studies Mars but is not involved in the project.

In 2002, NASA's Odyssey spacecraft discovered evidence of water ice - a possible signature of life - near the Martian surface in polar regions covered by permafrost. The area is similar to the broad, shallow valley where Phoenix will probe. NASA's twin rovers, Spirit and Opportunity, have uncovered geologic clues showing that water once flowed on Mars, but their range is limited to equatorial regions.

"There's nothing like getting ground truth information and seeing for yourself what's down there," Bell said.

Phoenix has traveled 422 million miles since its launch in August. Named for the mythical bird that rises from its own ashes, the spacecraft includes technology originally designed for previous Mars missions.

The thrusters and three supporting legs were designed for the Mars Surveyor 2001 mission, which was canceled after two previous spacecraft destined for the Red Planet were lost in 1999. They include the electronics that control the spacecraft, the 8-foot robotic arm that will do the digging, and the probes that look for evidence of water.

"There's been extensive testing of it and modifications to meet the specific science goals of the mission," Guy Webster, a spokesman for NASA's Jet Propulsion Laboratory in California, said of this spacecraft. The JPL is managing the mission.

But NASA officials were cautious when discussing Phoenix this week, given the space program's checkered history with the Mars. Despite the 2004 success of NASA's twin rovers - which unlike Phoenix used airbags to land on Mars - more than half the world's attempts to reach the planet have failed.

"The fact that we've been successful the last two tries is no guarantee of success. All of these things are fraught with risks," Goldstein said.

The airbags that successfully cushioned the much smaller rovers wouldn't work in delivering the 772-pound Phoenix. "We can deliver more mass to the surface with a thruster landing," Goldstein said.

The craft, sterilized to prevent Earth organisms from contaminating Mars, will search for evidence of ancient waterways, operate a weather station and search for organic compounds with optical equipment capable of studying details in particles hundreds of times smaller than the width of a human hair.

When the Phoenix lands just before 8 p.m. Eastern Time tomorrow, the spacecraft will wait 15 minutes for dust to settle before unfurling the 18-foot solar panels that produce its electricity. Cameras will rise on a 7-foot mast for panoramic views of the area, while sensors on a 4-foot mast will record temperature, wind patterns and other atmospheric data for a weather station designed by the Canadian Space Agency.

Using a powered drill bit at the end of its aluminum and titanium arm, Phoenix will work in eight-hour shifts, drilling up to 20 inches into a reservoir of ice, photographing the work progresses and unloading soil and icy debris onboard the craft's internal science lab. There it will be baked in ovens the size of a pencil shaft to see whether organic compounds - the building blocks of life - are in the vapors.

A key to the mission's success is the absence of rocks at the landing site - in a valley north of the planet's equivalent of the Arctic Circle.

NASA picked the site using the High Resolution Imaging Science Experiment camera on its Mars Reconnaissance Orbiter.

Another key tool used in the search was the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), operated by scientists at the Johns Hopkins Applied Physics Laboratory.

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