Credit: NASA/JPL-CALTECH/UNIV. ARIZONA

After a dramatic deceleration through Mars's thin atmosphere, NASA's Phoenix mission is set to go to work. It landed on 26 May about 30 kilometres from its intended set-down point in Mars's northern plains. Its arrival marks the first successful 'soft' landing on Mars — a gentle setting down by means of retrorockets, as opposed to a crash-bang-wallop arrival swaddled in airbags — since that of Viking 2, more than 30 years ago.

“This is a scientist's dream, right there on this landing site,” says mission principal investigator Peter Smith of the University of Arizona at Tucson, looking at pictures that show distinctive polygonal patterns on the surface (see right). Such patterning is one of the lines of evidence suggesting that Phoenix's digging arm should be able to unearth ice from the subsurface. The ice may record changes in the martian climate, and could contain organic molecules.

Mission scientists will spend a few days checking and calibrating instruments before starting to take samples for mass spectrometry and chemical analysis.

The successful descent was documented by a phenomenal image of the lander's parachute and shell (see inset), taken by the HiRISE camera on NASA's Mars Reconnaissance Orbiter during the descent from a distance of around 760 kilometres.