Phoenix on course for Mars.

NASA's Phoenix Mars Lander successfully accomplished on 10 August the first and largest of six course corrections planned during the spacecraft's flight from Earth to Mars.

Phoenix left Earth on 4 August, bound for a challenging touchdown on 25 May 2008, at a site farther north than any previous Mars landing. It will robotically dig to underground ice and run laboratory tests assessing whether the site could ever have been hospitable to microbial life.

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The second trajectory-correction manoeuvre is planned for mid-October. Without the correction manoeuvres, the spacecraft's course after launch day would miss Mars by almost one million kilometres--an intentional offset to prevent the third stage of the launch vehicle from hitting Mars. The launch vehicle is not subject to the rigorous cleanliness requirements that the spacecraft must meet as a protection against letting Earth organisms get a foothold on Mars.

Phoenix will be the first mission to touch water-ice on Mars. Its robotic arm will dig to an icy layer believed to lie just beneath the surface. The mission will study the history of the water in the ice, monitor weather of the polar region, and investigate whether the subsurface environment in the far-northern plains of Mars has ever been favourable for sustaining microbial life.

The Phoenix Mars Mission is the first of NASA's competitively proposed and selected Mars Scout missions, supplementing the agency's core Mars Exploration Program, whose theme is "follow the water." The University of Arizona was selected to lead the mission in August 2003 and is the first public university to ad a Mars exploration mission.

Phoenix uses the main body of a lander originally made for a 2001 mission that was cancelled before launch.

Samples of soil and ice collected by the lander's robotic arm will be analyzed by instruments mounted on the deck. One key instrument will check for water and carbon-containing compounds by heating soil samples in tiny ovens and examining the vapors that are given off. Another will test soil samples by adding water and analyzing the dissolution products. Cameras and microscopes will provide information on scales spanning 10 powers of 10, from features that could fit by the hundreds into a period at the end of a sentence to an aerial view taken during descent. A weather station will provide information about atmospheric processes in the arctic region.