“Darmstadt, Agilkia Base here…Philae has landed—kind of…”
Had the European Space Agency’s Philae lander carried a crew, those might have been the words uttered to ESA Mission Control in Germany as the spindly, three-legged lander ended a 10-year, nearly 4-billion-mile pursuit and gently made bumpy contact with the surface of Comet 67P/Churyumov-Gerasimenko, apparently bouncing at least once, rotating, and perhaps sliding along the ground.
The probe’s successful landing prompted online artists to extoll its precision, to compare its silhouette to Michael Jordan, and to create an entire series of comics narrating the final stages of its journey.
As the craft separated from the Rosetta main vehicle on November 12th and began a slow, seven-hour descent to the comet 14 miles below, a systems check revealed that a thruster mounted on top of the lander was not functioning. The thruster was supposed to counteract (or soften the blow of) the firing of two tethered landing harpoons into the surface, which would then have been used to reel Philae in and hold it securely to the comet. However, after touchdown, it was discovered that the harpoons hadn’t fired, either. Instead, the lander rested ever-so-tenuously in the region named Agilkia, completely unanchored.
In the extremely weak gravity of the comet, estimated to be about 1/10,000 that of Earth, the mini-fridge-sized spacecraft weighs only a gram. Under such tiny gravitational influence, it can easily be flipped over or blown off the surface by cometary outgassing. For now, however, as long as Philae sits on the surface, data are being collected by its instruments and relayed back to Earth by the orbiting Rosetta, revealing the magnetic and plasma environment of the comet, and—with any luck—an up-close look at the changes that occur on the comet as it approaches the Sun.
Because the harpoons contained instrumentation designed to measure the density of the comet’s crust, that type of information will not be available unless the harpoons can be redeployed, which—as of this writing—is a strategy being discussed.
For more information, check out ESA's website.
Images: ESA/Rosetta/Philae/CIVA; ESA/Rosetta/Philae/ROLIS/DLR; ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
Bing Quock is the assistant director of the Morrison Planetarium.