lander is ending tomorrow!
Phoenix will enter Mars's atmosphere at a speed of roughly 12,750 miles (20,520 kilometers) per hour. During the next "seven minutes of hell," it will slow from a combination of contact with the atmosphere, drag from a parachute and bursts from its thrusters [see animation below]. If it lands successfully, it would be the first craft to set down on Mars under its own power since the Viking 2 lander in September, 1976. NASA's last rocket engine–powered landing attempt—the Mars Polar Lander—crashed to its doom in December 1999.
As many people who follow these things know, placing a lander on Mars is not easy. Two thirds of such attempts fail.
What many people may not know, the Science Channel is broadcasting the landing live tomorrow!
Many people may also ask, why another lander?
Well, two things are of note about this lander:
First, if successful, the Phoenix Lander will be the first to successfully land on a polar region of Mars (in Phoenix's case, the north). These regions are of interest because of the water content in the form of ice, first verified by Mars Odyssey and the ESA's Mars Express orbiters.
Second, this will be the first lander since NASA's Viking Mission to land with a rocket thruster system.
Update
Twelve rocket thrusters will then slow the craft to 5 mph, echoing a scene from an episodes of Thunderbirds, and the probe's three legs make gentle contact with the planet's dusty floor. It will then embark on a search for signs of life in the reservoirs of ice beneath Mars's frigid north pole.
Also, the first lander since Viking to be equipped with a scoop to scoop up the martian regolith and perform an internal chemical analysis of the regolith.
The thruster touchdown is important -- in a system validation sense -- because the next Martian rover, the Mars Science Laboratory, will use a system that relies on rocket thrust as opposed to airbags to cushion its descent. The MSL's landing system will use a unique tether lowering system to set the lander down whole.
Like Viking, Pathfinder and the Mars Exploration Rovers, Mars Science Laboratory will be slowed by a large parachute. As the spacecraft loses speed, rockets will fire again, controlling the spacecraft's descent until the rover separates from its final delivery system, the sky crane. Like a large crane on Earth, the sky crane touchdown system will lower the rover to a "soft landing" -- wheels down -- on the surface of Mars, ready to begin its mission.
However, unlike the future MSL, which is in development, the Phoenix Lander is not a rover. It will stay in place on the surface once it's touched down.
What are they looking for?
Why, that's very simple. While the Phoenix Lander does not look for life itself, the poles are where the water is to be found close to the surface, and by analyzing the history of water on the Red Planet, that is also the history of life, or the possibility of life.
Update
celdd informs us that you can also see the status of the landing on NASA TV.