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Monday, August 6, 2007

Ice-seeking probe blasts off for Mars

Ice-seeking probe blasts off for Mars
A robotic dirt and ice digger blasted off Saturday on a 422 million-mile journey to Mars that NASA hopes will culminate next spring in the first landing within the red planet's arctic circle. e digger blasted off Saturday on a 422 million-mile journey to Mars that NASA hopes will culminate next spring in the first landing within the red planet's arctic circle

sions would have been able to do.

The unmanned Delta II rocket carrying the Phoenix Mars Lander rose from its seaside pad at 5:26 a.m., exactly on time, and hurtled through the clear moonlit sky. It was easily visible for nearly five minutes, a bright orange speck in a spray of stars.

If all goes as planned -- a big 'if,' considering only five of the world's 15 attempts to land on Mars have succeeded -- the spacecraft will set down on the Martian arctic plains on May 25, 2008. It will then spend three months scooping up soil and ice, and analyzing the samples in minuscule ovens and mixing bowls.

The Phoenix Mars Lander won't be looking for evidence of life on Mars but rather traces of organic compounds in the baked and moistened samples. Such compounds would be a possible indicator of conditions favorable for life, either now or once upon a time.

If organic compounds are present on Mars, they're more likely to have been preserved in ice. That's why NASA is aiming for the planet's high northern latitudes, where ice is almost certainly lurking just beneath the surface.

Only about six inches of soft red soil should cover the ice, and so the digger shouldn't have to probe too deeply. The ice is expected to be as hard as concrete, and a drill on the scoop will help gather enough frozen samples. Some dirt and ice samples will be baked and their vapors analyzed. Other soil samples will be mixed with onboard water and the muddy soup examined by onboard microscopes.

"We're really going there just to understand whether the conditions might have been hospitable for microbial life at some point," said the University of Arizona's William Boynton, lead scientist for the oven experiment.

Even if organic molecules pop up, they could be from incoming meteorites, Boynton noted. "It is important, I think, to keep in mind that we are just looking for organic molecules to see if the conditions are right that they could survive," he said, "and that we aren't really going to be making any inference about whether these molecules are indicative of life."

Mars landings are especially risky. Only five of the 15 U.S., Russian and European attempts have worked, all of them American successes beginning with the 1976 Viking touchdowns. Given those odds, the Phoenix team said it did everything possible to test for failures and will continue to do so as the spacecraft flies to Mars. The entire mission costs $420 million.

NASA has never attempted to land a spacecraft on Mars at such a high northern latitude. A lander intended for the red planet's south pole went silent immediately upon arrival in 1999. That failure, combined with the loss of the companion Mars orbiter, prompted NASA to cancel a 2001 lander mission. The parts from that scrapped mission were used for Phoenix -- thus its name, which alludes to the mythological bird that rises from its own ashes.

Mars' north pole would have been too cold for Phoenix to operate, and so scientists opted for a little lower latitude for touchdown. Phoenix will be shooting for 68.35 degrees north latitude, comparable to Greenland or northern Alaska, and 233 degrees east longitude. The lander will parachute down, with pulse thrusters easing its final descent.

Scientists chose the flattest, rock-free zone they could to ensure success. The target landing area is "Kansas flat," according to the spacecraft team, with few if any big rocks that could overturn the stationary three-legged lander or bump against its circular solar panels and jam them.

The 772-pound lander will stretch 18 feet across once its solar panels are deployed on Mars, and its weather mast will tower 7 feet. Watch how the lander will test the Martian soil »

Phoenix should help pave the way for human visitors, especially if it confirms the presence of water ice in large amounts near the pole, said Michael Meyer, NASA's lead Mars scientist. That would be a tremendous resource, he noted.

But if organic matter is indeed found, it could pose a quandary: "As Mars gets more interesting, you may not want to send humans right away until you learn out a little bit more about the red planet and find out whether or not life ever got started there."

Science fiction writer Kim Stanley Robinson, whose novel "Green Mars" is one of dozens of writings going up on a disk aboard Phoenix, is thrilled to see another robot headed to Mars.

The photos beamed back by recent Mars spacecraft "are just astonishingly precise compared to what I got to deal with when I was working on my books," he said. "It's like putting on glasses after you've been semi-blind all your life."

"I'm quite confident that humans will go to Mars and I do think it's important," Robinson said Friday. "When people get there, they'll be able to do on the ground what maybe 100 robotic missions would have been able to do.

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