During Wednesday’s historic landing on comet 67P/Churyumov-Gerasimenko, the European Space Agency (ESA) Philae lander suffered a setback that may cut its mission short. Due to equipment malfunctions, the unmanned, washing machine-sized lander failed to secure itself to the surface of the comet. In the 1/100,000 gravity, Philae bounced back into space twice, eventually landing in a hole about a kilometer (0.6 mi) from its designated landing area, where its batteries may not be able to charge properly.
The problems began during the powering up sequence before Philae separated from the Rosetta mothership on Wednesday morning. A fault was discovered in the cold-gas rocket system designed to keep the lander in contact with 67/P until its harpoons could fire and anchor it to the surface. However, mission control in Darmstadt, Germany, regarded the fault as minor enough to allow the landing to proceed.
At 15:34 GMT (lander time), Philae made contact with the comet after a seven-hour freefall descent. At first, the landing seemed a success except for some expected communication breaks, but later study of telemetry indicated that all did not go as planned.
As programmed, the screws on the feet of the lander’s legs tried to dig into the crust, but were unable to gain a purchase. Worse, for some still unknown reason, the harpoons failed to fire and Philae bounced back into space. It rose to an altitude of about a kilometer, then descended, bounced again at 17:25, rose to a much lower altitude, turned, then came to rest at 17:32 in a hole or crevice 6 ft (2 m) across and 6 ft deep.
ESA says that Philae is stable, but unanchored on the comet’s surface. It is lying on its side and has only two of its three legs in contact. Telemetry indicates that the lander was in shadow throughout the cometary night. However, its battery is charged, its instruments are functioning, and it is sending back the first close up images ever from a comet.
ESA scientists estimate that in its new position Philae is only receiving 1.5 hours of sunlight in 24 hours. If that is the case, the 60-hour charge in its batteries will run out no later than Saturday afternoon. The Philae team is currently studying its options.