In November, after the Philae probe's historic landing on a comet, it bounced and likely landed in a shadowy crater — quickly draining its battery due to a lack of sunlight.
As of yesterday, European Space Agency scientists still don't know exactly where it is, according to the BBC.
Over the last two months, scientists have used the Rosetta orbiter — which originally carried Philae to the comet 67P/G-C and is still orbiting the body — to take high-resolution photographs of the comet, manually poring over them for signs of the lander. But even though they have a rough idea of where Philae should be, they've been unable to find it.
Now, they're hoping that as the comet nears the sun in late spring, more sunlight will reach Philae's solar panels, allowing it to wake up and resume sending signals back to Rosetta.
How Philae got lost
When Philae landed on the comet — the first-ever controlled landing of a spacecraft on one — there were some technical difficulties. The most major one was that the probe's harpoons, which were designed to fasten it to the comet's surface, failed to fire.
As a result, Philae bounced several times. Due to the extremely low level of gravity, its first bounce took about two hours, and carried it as high as a kilometer above the surface. After another smaller bounce, it finally settled in a shadowy crater.
As a result, its solar panels were only able to collect about 90 minutes of sunlight every 12 hours, which meant the craft had to rely largely on its battery. Though ESA scientists used mechanical instruments on the craft to turn it slightly in hopes of getting more sunlight, the effort failed, and Philae powered down after 57 hours on the comet.
During this short interval, Philae sent back photos and data, making the mission as a whole a success. Among other things, that data has told us that the water present on the comet is different from that on earth, making it seem less likely that comets like 67P/G-C delivered water to earth billions of years ago.
But even though scientists were able to calculate the region of the 2.5-mile wide comet where Philae likely landed, photos taken by Rosetta have failed to reveal exactly where it is.
What's next for Philae
Rosetta has now ascended to a slightly higher orbit, and ESA scientists are no longer trying to use it to locate Philae. Instead, they're hoping that increased sunlight — the result of the comet's orbit bringing it closer to the sun — will provide enough solar power for the lander to wake up.
Yesterday, they said that this could happen sometime in May or June. By September, Philae could have enough power to begin using its scientific instruments once again, and continue collecting data.
The bad news, however, is that when the comet reaches its closest point to the sun — in August — excessive heat could make Philae inoperable. So even if the lander is indeed able to wake back up, there might be a fairly narrow window for it to conduct more science before shutting down for good.