Paris

Since Christmas Day, British mission controllers have listened in vain for a signal from their Beagle 2 Mars lander. Now the orbiter that carried the probe to the red planet is about to join in the search.

On 4 January, the Mars Express craft, operated by the European Space Agency (ESA), will begin sweeping the surface of Mars for radio signals from Beagle 2. The mother ship represents the best chance of finding out whether the lander survived its descent to the martian surface.

Beagle 2 was jettisoned by Mars Express on 19 December, a camera on board the ESA craft photographing the pocket-watch-shaped lander falling away on the final 3 million kilometres of its 400-million-km journey. It should have entered the martian atmosphere at around 20,000 km per hour at 2.45 am GMT on 25 December, before landing in the crater of Isidis Planitia about six minutes later, slowed to some 60 km per hour by parachutes and cushioned by airbags.

Just under three hours after that, mission controllers had hoped that Beagle 2's calling sign — a nine-note tune composed by the pop band Blur — would be picked up by NASA's Mars Odyssey craft, which has been orbiting the red planet since 2001. Over the days that followed, Mars Odyssey repeatedly tried and failed to make contact with the lander. The 76-metre Lovell radio telescope at the Jodrell Bank observatory in Cheshire, UK, and a 45-metre dish at Stanford University in California also drew a blank.

For the team behind Beagle 2, led by Colin Pillinger of the Open University in Milton Keynes, Beagle 2's silence has been frustrating. “This is a bit disappointing, but it's not the end of the world,” says Pillinger. Mars Express and Beagle 2 were designed to talk to each other, so the addition of the mother ship to the search party should give the best chance of detecting the lander.

Mars Express itself slipped into orbit in the middle of Christmas morning — an impressive result for ESA's first planetary mission. This weekend, mission controllers will fire the orbiter's engine for three minutes to nudge it from equatorial orbit into its final polar orbit, where it can begin operating on 4 January.

This new orbit will allow frequent passes over Beagle 2's landing area. At around the same time, the lander, which currently only broadcasts at set times, is programmed to switch to an emergency mode in which it will broadcast continuously during daylight hours.

Despite Beagle 2's high media profile — a product of Pillinger's gift for publicity (see Nature 423, 476; 2003) — Mars Express is the main part of ESA's mission. It carries a high-resolution camera to map the planet, a near-infrared spectrometer to assess surface mineralogy, radar to search for subsurface water down to a depth of 5 km, and instruments to study the planet's upper atmosphere and its interaction with the solar wind.

While the search for Beagle 2 continues, two NASA exploration rovers are also on their way to Mars (see Nature 423, 477; 2003). The first, Spirit, is also due to land on 4 January; the second, Opportunity, will touch down on 25 January.

→ http://www.beagle2.com

→ http://www.esa.int/mars