Officials wait for sign from Mars

DARMSTADT, Germany — European space officials on Wednesday tensely awaited the landing of their first probe on Mars, sending final commands to prepare its accompanying mother ship to start orbiting the planet as the Beagle 2 probe plunged toward the surface.

Beagle 2, which separated on Friday from the larger Mars Express orbiter, was expected to enter the Martian atmosphere and land at about 3:45 a.m. Christmas morning — Mission Control time — using parachutes and gas bags to cushion the impact.

At about the same time, Mars Express will fire its main engine for 34 minutes to slow it into orbit, a maneuver critical to the mission’s success.

But controllers will have to wait several hours or even days to pick up the first signals from Beagle 2, if it survives the fiery 7 1/2-minute plunge through the Martian atmosphere.

The 143-pound lander, shaped like an oversized wok, won’t communicate until it can open its solar panels and charge its batteries using the sun’s energy.

Confirmation that the Mars Express successfully entered orbit also won’t come for several hours, until it emerges from the far side of the planet.

Mission controllers sent the last commands to Mars Express Wednesday morning, telling it to heat its fuel tanks and switch off nonessential equipment so it won’t interfere with the maneuver.

"We have loaded the sequence and then we have switched off as many systems as possible — everything that is not absolutely needed," said mission control spokeswoman Jocelyne Landeau-Constantin. "Everything is going fine."

"From this point, the tension really starts to grow," flight director Michael McKay said. "We don’t have a lot more to do except watch and wait."

The first chance to hear from Beagle 2 — named for the ship that carried naturalist Charles Darwin on his voyage of discovery in the 1830s — comes Christmas morning in Europe when the U.S. Mars Odyssey spacecraft, already orbiting the planet, has a chance to pick up and relay a signal.

If that doesn’t work, the Jodrell Bank Observatory in Britain will try to pick up Beagle’s signal later Christmas Day.

Mars Express’ entry to orbit is critical for the mission, since the mother craft will relay Beagle’s scientific data back to earth.

It won’t be in position to make contact with Beagle until Jan. 3 because its initial orbit is too high and will have to be corrected.

Beagle is designed to use a robotic arm to sample surface rock and soil for signs of past or present life.

Meanwhile, Mars Express will orbit overheard for at least a Martian year, or 687 Earth days, probing as deep as 2.5 miles below the surface with a powerful radar to look for underground water. It will also map the surface with a high-resolution stereo camera.