The Philae lander traveled for more than a decade atop the European Space Agency's Rosetta spacecraft to arrive at Comet 67P/Churyumov–Gerasimenko. But after that long journey, landing didn't go so smoothly. Philae bounced off the comet, flew for two more hours, and then crashed back down.
Scientists couldn't figure out exactly where Philae ended up on the comet – until now.
The lander is wedged into a dark crack in a region called Abydos, on the smaller lobe of the lumpy comet. And its location explains why Philae had been so difficult to locate and communicate with.
"The position, as we find in this image, did not help at all," Patrick Martin, ESA's Rosetta Mission Manager, told The Verge.
Philae is powered by solar panels, which wouldn't have received much sunlight in a dark crevice, and its antenna seem to be pointing toward the comet rather than out to the Rosetta spacecraft orbiting the space rock.
The lander didn't lose contact right away after landing. Philae's battery lasted three days before the lander went into hibernation. When the comet swung closer to the Sun, it booted up again and communicated briefly with Rosetta before going dark again.
Finding Philae's precise location will help scientists sort out that data, says Matt Taylor, ESA's Rosetta project scientist, in an ESA press release. "This wonderful news means that we now have the missing ‘ground-truth’ information needed to put Philae’s three days of science into proper context, now that we know where that ground actually is!"
Even with just a few days worth of data, Philae filled in a few key puzzle pieces for scientists. The lander found that Comet 67P doesn't have a magnetic field, which was thought to be a potential explanation for the formation of small bodies in the solar system. The lander also found 16 organic compounds on the comet, among other intriguing substances.
The Rosetta mission scientists have been hunting for Philae since it touched down on the comet on November 12, 2014. Although scientists had narrowed in on a region, the two-year hunt required a closer look from Rosetta. Scientists got their chance on September 2, when the orbiter came within 1.7 miles of the surface.
In the clearer new images, the scientists were able to pick out the body of the lander and two of its three legs.
The discovery comes just as scientists are pulling the plug on Rosetta. The orbiter is set to crash onto the comet's surface at the end of the month, snapping closeups of the surface of the comet as it goes down.
Despite finally spotting Philae, scientists won't hear any more from the lander. In July the ESA turned off the system Rosetta uses to communicate with Philae as part of the process of preparing for the end of the mission.
"Psychologically it’s giving us closure now," Dr. Taylor told The Verge.
Dr. Martin adds in the press release. "We were beginning to think that Philae would remain lost forever. It is incredible we have captured this at the final hour."