Why is it called 2001 Mars Odyssey?

It was inspired by 2001: A Space Odyssey, the movie written by Arthur C Clarke and Stanley Kubrick, a movie that had nothing to do with Mars.

How far has it travelled to get to Mars?

The craft has travelled 460 million km (286 million miles) in six and a half months.

How big is it and how much did it cost?

The 725 kg (1,598 pound) unmanned satellite is 2.1 metres (7.2 feet) long, 1.7 m (5.6 feet) tall and 2.6 m (8.5 feet) wide. It cost $297 million (�209 million).

What happens now the probe has entered the orbit of Mars?

The probe will gradually settle into a circular orbit at an altitude of some 400 kilometres (250 miles) above the Martian surface. The adjustment happens by a series of delicate breaking manoeuvres, called aerobraking.

What scientific observations will it carry out?

The probe is carrying a gamma ray spectrometer, which includes a high-energy neutron detector, as well as a thermal-emission imaging system and a Martian radiation environment experiment. It will use these instruments to carry out a chemical and mineralogical survey of the planet. It will also look for hidden reservoirs of water and assess radiation risks to future human missions. Mars Odyssey is expected to start mapping the surface of Mars in January.

How long is the mission?

Mars Odyssey's primary scientific mission lasts from January 2002 to July 2004 but if it remains in good order it would be extended.

The spacecraft also will serve as a communications relay for US and international spacecraft in 2003 and 2004.

What other missions are planned?

Twin American surface rovers are planned for 2004 as well as a British lander called Beagle 2, which is set to land on the planet in next three years. Further Mars orbiters are planned for after that and then, hopefully, a sample return mission.