Philae, the brave little comet lander that captured our hearts last year, has probably fallen silent for good. After a final, desperate effort to contact the spacecraft over the weekend didn't pan out, the German Aerospace Agency (DLR) reports that the chances of ever speaking to the probe again are slim — and they're growing slimmer every day. Landing the Philae probe on Comet 67P/Churyumov-Gerasimenko, a frigid ice rock located some 510 million kilometres from Earth, was one of the biggest spaceflight achievements of the decade. But it didn't go off perfectly. When the lander touched down in November of 2014, it bounced twice, and wound up in the dark shadow of a cliff. Without enough sunlight to charge its solar panels, Philae quickly exhausted its power supply. Within 57 hours, it had fallen silent.
Six months later, as Comet 67P approached the sun, Philae briefly woke from its slumber and phoned home. Then, it went quiet again. The DLR's Philae team hasn't heard a peep since.
Comet 67P reached perihelion, its closest approach to the Sun, in August, and since then it's been speeding away. By the end of January it will be so far out that Philae won't be able to charge up at all. With the clock ticking, the DLR's lander team made a last-ditch attempt to stir the probe into wakefulness on Monday (Sunday in the US). They sent a blind command via Rosetta (the orbital spacecraft that deployed Philae to the surface) telling Philae to spin its flywheel. If that wheel could be jostled, it might shift the lander's position enough to give it a few last rays of sunshine.
Sadly, Rosetta's command didn't seem to phase the frozen comet lander. But it isn't entirely clear why Philae didn't respond, according to Philae project manager Stephen Ulamec.
"We did not get a signal, so we do not know whether either the command has not been received, or if there is not enough power at the lander, or whether the communications unit is damaged," Ulamec told Gizmodo in a phone interview. "So we did [a few commands] yesterday and will continue to do a few more commands."
These commands include an attempt to switch on Philae's radar system. According to Ulamec, if the comms system is busted, there's still a chance Rosetta could pick up a radar signal. "But we've done this several times before and it hasn't been successful," he added.
As another final check, the DLR is analysing photos of Philae's crash site taken by Rosetta's OSIRIS camera. If Philae kicked up any dust on 67P's surface over the last few days, it could be a sign that the lander received the flywheel command. "Until now, we didn't see any indication, but a few people are continuing to look," Ulamec said. Gizmodo has reached out to the team analysing the OSIRIS images, but have not yet heard back.
But for final closure on the Philae lander situation, we may have to wait until winter. As the Rosetta orbiter draws in closer to 67P, it will snap our best photos yet of the comet's surface. "We hope to get higher resolution images of the lander on the surface, and we'll learn a lot more then," Ulamec said.
Its science career may have been cut short, but the European Space Agency still considers the Philae lander a huge success. During its brief period of activity on 67P's surface, Philae managed to analyse some samples and relay the data to the Rosetta orbiter. Among other things, these samples provided verification that organic molecules — the building blocks of life — are present on the comet's surface. Meanwhile, Rosetta has performed beautifully, collecting troves of valuable data over the past year.
"People are all very sad now, but we should not be so sad about what we couldn't achieve and be happy about all the data we could get after the landing," Ulamec said. "Which was fantastic."
Top: Artist's concept of Philae on the comet, via ESA