European, American, and Australian scientists are pointing their radio telescopes at Mars, hoping to hear a signal from the Beagle II Martian probe.

The British-built Beagle was supposed to have landed on the red planet Thursday, and send a signal back to Earth. Anxious engineers at the European Space Agency have heard nothing so far.

British scientists have split up into two teams, one to keep listening for a signal and the other to investigate possible reasons why the Beagle has not responded.

European Space Agency officials say they have not given up and believe the Beagle is somewhere on the Martian surface. They say the Mars Express orbiter, which is circling the planet, will change its orbit later this week and be in a better position to pick up a signal from the Beagle.

The Beagle II is supposed to probe the Martian surface and atmosphere for signs of life. Two U.S.-built probes are scheduled to land on Mars next month.