The European Space Agency made history on Wednesday when they soft-landed a spacecraft on the surface of a comet for the first time ever. The Philae lander was launched inside the Rosetta spacecraft in 2004, and the pair traveled 6.5 billion kilometers in order to catch up with Comet 67P/Churyumov-Gerasimenko to make that landing a reality. Philae has already started collecting and returning the first science data, but the lander’s one to six-week-long projected mission is already facing some serious problems.
In one of the final go/no-go checks before Philae detached from Rosetta, the team discovered that one of the thrusters was not working properly. Though this was a problem, there was nothing the team could do to fix it and the detachment was given a go. Seven hours after detachment, Philae first arrived at Agilkia, the designated landing site.
ESA reports that Philae bounced twice after making initial contact with Comet 67P/C-G. The first bounce could have been as high as a kilometer, sending the lander airborne for about two hours. The second bounce was much smaller and only lasted about 7 minutes. ESA scientists aren’t entirely sure where Philae is now, though it is believed to be roughly a few hundred meters from the original landing site.
The comet’s gravity might have been enough to pull Philae to its surface, but it likely isn’t going to be enough to keep it there. The lander has three legs that were fitted with ice screws, intended to stabilize Philae onto the comet’s surface. The thruster was supposed to push the ice screws into the comet, temporarily holding the lander in place until the harpoons fired to anchor it securely.
ESA confirmed the harpoons did not fire and telemetry suggests that only two of the three legs are in contact with the ground, leaving the spacecraft tilted on its side. The comet is currently barreling toward the Sun, increasing the amount of ice and dust being shed off. This leaves Philae in an undesirable predicament, because there is no telling how long it will be able to hang on.
Despite the anchoring issues, the instruments on board appear to be functioning properly and are transmitting sufficient data and images. Philae sent back a panoramic photo of its location, which appears to be at the edge of a cliff. If the lander is where ESA thinks it is, the lander likely isn’t in an area that will receive adequate sunlight for the solar panels to recharge its secondary battery. With the charge it has now, there is enough juice to last until Saturday morning, depending on how many instruments it uses. With the anchoring issues, the scientists might be tempted to just do as much as they can in the time they have, but that will just run down the battery faster.
While Philae’s future is currently uncertain, the fact that ESA has been able to collect the first scientific measurements directly from the surface of a comet is a tremendous achievement that will provide invaluable data.