Phoenix Spacecraft Nears Mars Touchdown
By Art Chimes
22 May 2008
The U.S. space agency's latest mission to Mars, NASA's Phoenix Lander spacecraft, is on its final approach to the Red Planet. If all goes well, it will touch down at 23:53 UTC Sunday night and soon begin digging beneath the surface looking for signs of water and other evidence that life might have once existed on Mars. VOA science reporter Art Chimes has this preview of the first attempt in five years to put a lander on Mars.
The Phoenix Lander mission is by no means a sure thing. In 1999, a nearly identical spacecraft, called the Mars Polar Lander, apparently crashed on the Martian surface.
The most recent successful landings on the planet were the Mars rovers, Spirit and Opportunity. They each came down hard, the landings cushioned by air bags. Phoenix, however, is too heavy for that, so it will land the old-fashioned way, with its descent first slowed by a parachute, and then by retro-rockets.
NASA official Ed Weiler admits the track record for Mars landings is not great.
"Fifty-five percent of all human attempts to land robots on Mars have failed," he told reporters at a NASA briefing. "The U.S. has a better record, as we have succeeded in five of six attempts. But three of those five successes employed air bags. Viking was the last time we successfully used retro-propulsion and landing legs, so it has been over 32 years since NASA has been successful in such a landing."
Scientists working on the Phoenix project think the $420 million mission is worth it. Doug McCuistion heads NASA's Mars Exploration Program. He says this mission is all about the water.
"It's the first lander to the Martian arctic. And it's also the first mission that's actually going to touch the water. The program's mantra has been 'follow the water.' This time Phoenix actually is going to touch it for the first time."
Water, of course, is an essential component of life as we know it. It would also come in handy whenever humans finally visit the Red Planet.
The seven-year-old Mars Odyssey satellite, which is orbiting Mars, has identified water under the planet's surface. The Phoenix mission's principal investigator, Peter Smith of the University of Arizona, says it's mostly frozen water, ice, mixed in with the soil, at higher latitudes, which is where Phoenix is landing.
"And so we expect a tremendous abundance of ice in these northern plains, and in fact our landing site is in the highest concentration of ice outside the permanent polar caps," Smith said.
The landing site is at 68 degrees north latitude - comparable on Earth to northern Sweden, only a lot colder.
Phoenix is scheduled to spend at least three months digging up bits of Martian soil with its two meter-long scoop and studying them with on-board science instruments. Samples will be vaporized and analyzed with a mass spectrometer. A pair of microscopes will beam detailed images back to Earth, where scientists will see if structures in the rock provide evidence of liquid water in the Martian past. There's also a compact weather station to track changes in temperature, pressure and blowing dust and ice particles.
Unlike the twin Mars rovers that have ranged across kilometers of the Martian landscape, Phoenix will remain in one place. The rovers, incidentally, are still working, four years after starting what was originally designed to be a three-month run around the Martian surface.
The Phoenix scientists are interested in knowing whether Mars - or at least this region of the planet- has some of the raw materials of life.
"Our highest goal," Smith stressed, "is to see if this creates a habitable zone on Mars, where we might find organic materials. We might find the presence, at least periodically, of liquid water, and we might find chemical energy sources."
After the failure of the Mars Polar Lander nine years ago, scientists and technicians will be holding their breath as Phoenix enters the Martian atmosphere. Unlike the Polar Lander, Phoenix will have what project manager Barry Goldstein calls "robust" communications during the final entry, descent and landing (EDL) stage.
"And the reason I say that is, what's most important is that, even in the untoward event that we fail - which is, obviously a possibility, hopefully not a probability - the important thing to me is that we learn something from this."
In the first hours of Monday morning UTC, engineers at NASA's Jet Propulsion Laboratory in California should get radio transmissions from Mars - which take about 15 minutes to travel to Earth - telling them if the Phoenix spacecraft landed safely.
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