Phoenix mission on the launch pad
Reincarnated martian lander goes in search of water.
A mobile laboratory should leave for Mars this weekend, aiming to dig up water ice from beneath the planet's surface.
NASA's Phoenix mission is scheduled to launch from the Kennedy Space Center early in the morning of Saturday 4 August. Bad weather has delayed the launch by a day.
Brandishing a digging arm and a range of scientific instruments, Phoenix is headed for an area of the martian north polar region thought to be rich in subsurface water ice, which was spotted by NASA's Odyssey spacecraft in 2002.
The craft will have a soft landing on a relatively flat, featureless terrain. The landing is crucial, as Phoenix is an updated version of the Mars Polar Lander, which lost contact with Earth just as it was getting ready to touch down in 1999. Phoenix also contains elements of NASA's Mars Surveyor mission cancelled in 2000.
Phoenix has a heat shield to protect it as it enters the Martian atmosphere, a parachute to slow its descent and — a new development — small rockets to guide it gently to the surface. NASA has asked the European Space Agency's Mars Express spacecraft, which is in orbit around the planet, to train its camera on Phoenix and monitor the descent.
If all goes well, when it arrives on 25 May 2008, Phoenix will spend the first week settling into its new home. First, it will check that its solar panels, meteorological monitoring station and digging arm are properly deployed.
Next up will be a single-colour shot of the panorama, followed by tests of its instruments, which include a mass spectrometer, a number of different cameras, and an analyser that can do atomic force microscopy and electrochemistry, and measure conductivity.
"Then we start digging," says Deborah Bass, Phoenix deputy project scientist at the Jet Propulsion Laboratory in Pasadena, California. Samples from the top layer of soil will be analysed for their mineralogical content and a trench will be dug in search of water ice. Bass hopes to find it between 2 and 10 centimetres below the surface, but the 2.4-metre-long arm can dig down 50 cm, she says.
The trench will also help to give an idea of Mars's changing chemical make-up over geological timescales. The meteorological station will monitor temperature, clouds and dust on Mars, to see if and how water changes from ice to vapour on the planet.
The mission is planned to take 90 days, but could last up to 150 days before it succumbs to the martian winter. There's very little chance the instruments could survive Mars's carbon-dioxide frosts.
Nevertheless, the Phoenix scientists will attempt to contact their craft the following spring. But they aren't optimistic: "the likelihood of it staying alive is small," says Bass.