The final resting place of the European Space Agency's (ESA) Philae comet lander is no longer a mystery. After a nearly two-year search, the agency has finally managed to locate the lander's grave on Comet 67P/Churyumov-Gerasimenko — a discovery that comes with only a month left in the current Rosetta mission.
"This remarkable discovery comes at the end of a long, painstaking search," Patrick Martin, ESA's Rosetta Mission Manager, said in a statement. "We were beginning to think that Philae would remain lost forever. It is incredible we have captured this at the final hour."
Philae made history on Nov. 12, 2014, when it became the first vehicle to land on a comet, however, the way it did was not quite as expected. The lander was supposed to deploy harpoons that would allow it to anchor itself to the comet and perform its duty. However, those harpoons failed to fire and Philae bounced off the comet instead, flying for about two hours before landing in a then-undetectable location.
For what it's worth, Philae did manage to do some work — about 60 hours' worth — thanks to it being solar powered, but those reserves soon dried out and it went into hibernation mode. The ESA was hopeful that Philae might receive enough sunlight again once the comet got closer to the sun on its orbit, and that seemed to be the case in summer of last year. The Rosetta spacecraft, which started its search after Philae's landing, picked up some signals from Philae throughout June and July of 2015, but didn't hear from the lander since.
Now, things have taken a turn for the better. In images dated Sept. 2, a time when Rosetta shortened its orbit above the comet to about 1.7 miles, the ESA was finally able to locate an object that they could definitively say was the missing Philae lander.
The location? A crevice, eclipsed by the shadow from a larger boulder above it.
With this discovery, everything that happened since the lander disappeared suddenly makes perfect sense. Because the lander was draped in the shadow of a large boulder, it was impossible for it to receive enough sunlight to sufficiently function for an extended period of time. Furthermore, because of its awkward landing position — with the antenna pointing toward the rocks, rather than toward space — it was near impossible for Rosetta to pick up any signals from it, any signals that it did pick up were quite weak.
Unfortunately, even though the ESA does know the location of Philae, there isn't much they can actually do about it. In July, the agency turned off Rosetta's Electrical Support System Processor Unit, the system that the spacecraft uses to communicate with Philae, in preparation for the end of the Rosetta mission on Sept. 30.
However, even if they can't do anything about it, there is still two things that can be gained from the discovery. First, researchers can put the lander's scientific observations in context with the vehicle's surroundings. Second, it allows the ESA to finally lay to rest a mystery that has burdened the agency for the past two years.
"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," said Matt Taylor, ESA's Rosetta project scientist.
