Defunct Philae found on the surface of the comet

As Rosetta’s mission draws close to an end, its high-resolution camera snapped a few photos of the Philae lander, wedged into a dark crack on Comet 67P/Churyumov–Gerasimenko.

In August 2014, the Rosetta spacecraft became the first man-made object to interact with a comet from close range. It performed a series of maneuvers which allowed it to enter the comet’s orbit, and from there made several important observations, transmitting a trove of valuable data back to Earth. But the European mission was even more ambitious than this: they sent a lander to the surface of the comet.

The Philae lander detached from Rosetta on 12 November 2014 but things didn’t go as smoothly as possible. The landing was a bit odd, with Philae failing to launch one of its anchoring harpoons. A thruster designed to hold the probe onto the surface also didn’t fire, and the probe bounced off the surface twice. After this, Philae did manage to land on the comet, but it really wasn’t the optimal land we were hoping for.

The land left it in a less-than-ideal position in a shaded area. Its battery ran out of power 3 days later, and because it lacked access to sunlight it couldn’t really power up again. Rosetta’s communications module with the lander was completely turned off on 27 July 2016 and we’ve known nothing of the probe ever since – it was completely silent.

But now, with one month left of the Rosetta mission, the craft spotted Philae again.

“With only a month left of the Rosetta mission, we are so happy to have finally imaged Philae, and to see it in such amazing detail,” says Cecilia Tubiana of the OSIRIS camera team, the first person to see the images when they were downlinked from Rosetta yesterday.

“After months of work, with the focus and the evidence pointing more and more to this lander candidate, I’m very excited and thrilled that we finally have this all-important picture of Philae sitting in Abydos,” says ESA’s Laurence O’Rourke, who has been coordinating the search efforts over the last months at ESA, with the OSIRIS and Lander Science Operations and Navigation Center (SONC, CNES) teams.

The team had been actively searching for Philae for months, but it wasn’t an easy job. At the camera’s resolution of 5 cm/pixel, this was just barely enough to reveal features of Philae’s 1 m-sized body and its legs, as can be seen in this image.

“This remarkable discovery comes at the end of a long, painstaking search,” says Patrick Martin, ESA’s Rosetta Mission Manager. “We were beginning to think that Philae would remain lost forever. It is incredible we have captured this at the final hour.”

“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!” says Matt Taylor, ESA’s Rosetta project scientist.

The discovery comes less than a month before Rosetta descends to the comet’s surface. At the end of this month, on 30 September, Rosetta will be sent on a one-way mission to investigate the comet from close up.