Mute Mars Probe Miffs Scientists
Scientists struggled to understand Sunday why they have failed to make contact with Europe's first Mars probe, four days after the Beagle 2 craft was supposed to touch down on the Red Planet to begin its search for life.
Repeated attempts to pick up the vessel's call sign have struck out, but Beagle's creators say they're still hopeful of hearing from the lander.
NASA's Mars Odyssey, which is orbiting the planet, again passed over the spot where scientists believe the probe touched down on Christmas Day. But it failed for a fourth time to pick up a signal from Beagle. Another overflight is scheduled for Monday.
Project leaders say, however, that their best hope of contacting Beagle will come when its mother ship, Mars Express, enters a low polar orbit on Jan. 4.
"That is the communication line that has been tried and tested," said Gill Ormrod, spokeswoman for the British government's physics and astronomy research agency. "Until they have tried that several times, they will not give up."
Mars Express, which carried Beagle into space and set it free more than a week ago, is currently orbiting the planet as high as 117,00 miles above its equator.
On Tuesday, European Space Agency scientists at mission control in Darmstadt, Germany, will fire Mars Express' engine in an attempt to shift its orbit. They hope to move it over one of the Martian poles — necessary for it to survey the entire planet with its high-resolution camera and a powerful radar that can look for underground water.
Scientists hope to gradually reduce the polar orbit and say that by Jan. 4, Mars Express should pass as low as 125-155 miles above the surface, enabling it to take close-up pictures and listen for Beagle.
The team at Britain's National Space Center in central England was striving Sunday to understand why it had so far failed to hear Beagle's call sign from the Martian surface.
Within hours of landing, the 143-pound probe, which has a robotic arm to take soil and rock samples, was supposed to unfold its solar panels and transmit a signal confirming its arrival.
But Britain's vast radio telescope at Jodrell Bank Observatory has failed three times to detect the probe in sweeps of the planet's surface.
Scientists at Stanford University, California have also joined the hunt, using a 150-foot dish antenna to listen for transmissions from the probe. They found nothing early Sunday. Team member Alan Wells said an "analysis and recovery think tank" was trying to understand what may have gone wrong.
"One possible explanation that has been raised for the apparent silence is the potential for incompatibility between the systems on board Beagle and those used by Mars Odyssey," he said in a statement.
Scientists also believe the probe may have landed off course in an area where communication is difficult. They say its antenna may not be pointing in the direction of Odyssey and also fear Beagle's onboard clock has suffered a glitch, resulting in the probe sending signals at the wrong times.
Even if the Beagle fails to transmit its call sign, Wells said the Stanford radio telescope could also scan the surface for low levels of radiation emitted by the probe.
"This might be considered comparable to looking for signs of Beagle's heartbeat, rather than listening for its bark," he added.
Getting a working spacecraft to Mars has proven frustratingly difficult. Several vehicles, most recently NASA's 1999 Mars Polar Lander, have been lost on landing. The Soviet Mars-3 lander touched down safely in 1971 but failed after sending data for only 20 seconds.