Philae's touchdown in November went awry, leaving the lander in a dark and somewhat mysterious location, operating on battery power alone. After 60 hours, the battery died and Philae went silent. Although the lander got in touch with the Rosetta orbiter a few times last summer, the comet is now moving farther and farther from the sun. That's not good news for Philae, since it needs solar power to charge, and the comet freezes over with night temperatures of -180 degrees Celsius--too cold for the lander to function. Philae's ensuing silence now is likely due to failing transmitters and receivers and a coating of dust on its solar panels.