Mars Weather Looks Good for Phoenix Probe's Sunday Landing

PASADENA, Calif. — It?s going to be a nice day on Mars when NASA?s Phoenix Mars Lander makes its planned touchdown in the northern plains of the red planet on Sunday, mission engineers said Thursday.

?The weather is good for our landing on Sunday, no dust,? said Phoenix principal investigator Peter Smith of the University of Arizona. ?We are ready to explore the northern plains of Mars.?

Now in the homestretch of its 422 million-mile (679 million-km) trek to Mars, Phoenix is just 77 hours away from its May 25 landing, mission managers said during a briefing here at NASA?s Jet Propulsion Laboratory (JPL).

Phoenix is slated to land on the artic plains of the Vastitas Borealis region of Mars, where it will dig down into the rock-hard layers of water ice thought to lie under the Martian soil near the planet?s north pole.

Mission scientists had been monitoring a dust storm in the vicinity of Phoenix?s planned landing site, but determined it won?t pose a problem during the craft?s descent through the Martian atmosphere, Smith said.

The $420-million mission launched in August with some of the same instruments originally designed for its ill-fated predecessor, the Mars Polar Lander that crashed in 1999, and is aimed at testing the Martian soil and ice to see if it could have created a habitable zone for primitive life at some point in the past. The probe carries a shovel-tipped robotic arm, ovens and a wet chemistry lab to study Mars ice samples.

Mission scientists hope to receive the signal that Phoenix has landed on Sunday at 7:53 p.m. EDT (2353 GMT) - there will be about a 15-minute delay between landing and when the signal reaches Earth because it must travel the 171 million miles (275 million km) between the two planets.

But before Phoenix can begin its science mission, ?it has to go through one of the most risky phases of its landing, the entry descent and landing,? said Fuk Li, NASA?s Mars Exploration Program manager at JPL. ?It will be a nerve-wracking time on Sunday for all of us.?

While mission scientists are optimistic about Sunday?s planned landing, they acknowledge that there is no guarantee of success. Mission engineers are hoping they?ve worked out all the problems that were encountered with the lost Mars Polar Lander (MPL) in 1999, which used a similar landing system to Phoenix, but failed during descent through the Martian atmosphere.

Mission scientists say the craft has performed fine so far with all course adjustments and in-flight testing, even skipping one trajectory correction since it?s been flying so true.

?We?ve had a very clean flight to Mars so far,? said Ed Sedivy, Phoenix spacecraft manager from Lockheed Martin Space Systems. ?The spacecraft has been very well-behaved.?

Phoenix?s next possible maneuver will come on Saturday at 10:46 p.m. EDT (0246 May 25 GMT) with an opportunity to adjust the adjust the craft?s course toward the Martian arctic by firing its thrusters.

If all goes according to plan, Phoenix will land somewhere in an elliptical area at 68 degrees north latitude, 233 degrees east longitude.

To make successful landing, the spacecraft will have to endure a harrowing seven-minute descent through the Martian atmosphere, which Li and the other mission scientists described as the most difficult part of the whole mission.

Friction at the beginning of its fall will heat the craft?s heat shield to a scorching 2,600 degrees Fahrenheit (1,420 degrees Celsius). Phoenix?s parachute should deploy once the probe is at an altitude of about 7.8 miles (12.6 kilometers) above the Martian surface. During the next three minutes of the fall, the heat shield will be jettisoned and the legs will extend. Thrusters should kick in when touchdown is just 40 seconds away to slow the lander into its planned soft landing.

The last successful landings on Mars were NASA?s two Mars Exploration Rovers Spirit and Opportunity, but those craft used airbags to cushion their landing, not thrusters. The thruster technique that Phoenix will use has not been used successfully since NASA?s two Viking missions set down in 1976.

NASA scientists hope that Phoenix will follow the successes of the two rovers and other successful missions. If all goes well, ?on Sunday, we?ll be welcoming to this family a new family member, the Phoenix Mars Lander,? Li said.

NASA's broadcast Phoenix Mars Lander events live on NASA TV, with the next mission briefing set for 3:00 p.m. EDT (1900 GMT) on Saturday, May 24. Click here for SPACE.com's Phoenix mission coverage and a link to NASA TV.

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