Scientists unsure if Beagle has landed
Artist's view of Beagle 2's airbags separating to release the lander on the Martian surface
CNN's Gaven Morris on the Beagle 2 probe and its failure to signal from Mars.
Final commands are sent to the twin crafts in Europe's first Mars mission.
(CNN) -- Europe's effort to successfully land its first probe on Mars has suffered a setback.
The British-built Beagle 2 probe has failed to broadcast a signal to confirm it has landed on the red planet.
Landing was supposed to have happened at 21:54 p.m. ET (02: 54 GMT), but it is not yet known whether it survived the dangerous touchdown.
If its parachute opened, its airbags deployed and its outer cocoon bounced to a halt as planned near the Martian equator, the 140-pound probe was to hail NASA's Mars Global Surveyor orbiter when it passed overhead.
Scientists say they still hope to eventually hear from Beagle 2, whose mission is to see whether there is life on Mars.
Professor Colin Pillinger told a press conference Thursday morning the lack of signal does not necessarily mean failure and offered five possible scenarios:
• The spacecraft landed in the wrong place
• The craft's transmitting antenna landed disoriented and cannot fully open
• There is a communications mis-match between NASA's orbiting Mars Global Surveyor and Beagle 2
• A failure during entry descent damaged the spacecraft
Scientists will try again to hail the probe Friday 18:00 GMT, the next best window of opportunity.
Confirmation of a safe landing would come in the form of a nine-note musical signal from Beagle 2, written by the British pop band Blur.
Riding with the mother ship
The mission includes Beagle 2 and the Mars Express mother ship, which will remain in orbit to look for signs of water below and on the Martian surface using ground-penetrating radar, infrared and other instruments.
If Beagle 2 fails to communicate with Surveyor during a window that lasts about 15 minutes, it could make radio contact later in the day with the Jodrell Bank Observatory in the United Kingdom.
The mini-lander hitched a six-month ride to the red planet with the Mars Express, which on Friday dispatched Beagle 2 on its way to Isidis Planitia, Martian lowlands in a basin that may have contained water several billion years ago, when the planet was thought to have been warmer and wetter.
For 180 days, mission planners hope, Beagle 2 will look for evidence of past or perhaps current microbial life. It will drill nearby rocks, dig into the soil and sniff the air, looking for organic matter and other life-related chemical compounds like atmospheric methane.
To search for samples, the stationary droid will use camera eyes to guide a robot arm to a suitable rock. It will then drill and retrieve a core sample from the interior of the rock and place it under intense heat in the presence of oxygen.
The chemical cooking should allow Beagle 2 to look for telltale signs of organic compounds. Different carbon-bearing materials burn at different temperatures, according to Beagle 2 scientists.
"There is no hope of finding carbonaceous compounds (associated with primitive, microscopic life) on the surface because it's all been burnt by the sun," Beagle 2 scientist Andre Brack said earlier in a statement. "There's no protective magnetosphere or ozone later in the Martian atmosphere."
Surviving the 'death planet'
The robot ship, named for the sea vessel that carried famed biologist Charles Darwin around the world in the 19th century, is the first of three visitors that Mars may host over the winter holidays. Two identical NASA mobile landers are expected to arrive weeks apart in January.
The rover twins, named Spirit and Opportunity, will analyze rock and soil samples on the surface, traveling up to 110 yards a day as they look for evidence that liquid water once flowed on Mars.
Despite their differences, the U.S. and European missions have some common features. All will land with a bounce, cushioned by inflatable airbags. Both will use grinders to remove the weathered surface of rocks and expose their pristine interiors.
Just reaching the red planet would be a milestone. Of about 30 attempts to reach Mars, two-thirds have ended in disaster. Of nine attempts to land, only three have succeeded.
"A lot of people have had bad days on Mars. They don't call it the death planet for nothing," Ed Weiler, NASA deputy administrator, said earlier this year.
NASA has the best record. All three landings were by U.S. missions. But the U.S. space agency lost two Mars-bound craft in 1999. One likely crash-landed and another burned up in the atmosphere, presumably because of a mix-up over metric and English propellant measurements.
The latest casualty was Japan's Nozomi orbiter, a trouble-plagued craft that took years longer than expected to reach the Mars system. Earlier this month, as it neared the red planet, project engineers said that persistent electrical and communication problems had doomed the mission.
-- CNN's Richard Stenger contributed to this report