Being lost in space is usually a permanent condition. That is, unless you’re the European Space Agency’s Philae lander, a critical component of the comet-chasing Rosetta mission. Philae has been missing since its unexpectedly bumpy touchdown on comet 67P/Churyumov-Gerasimenko in November 2014, but on September 5th, scientists finally found what they were looking for.
In a photo taken by Philae’s mothership, the Rosetta orbiter, you can see the probe wedged in a crevasse, its landing legs sticking up in the air like an overturned beetle’s. Well, if you squint, anyway. Philae’s one-meter body is pretty hard to spot. In fact, scientists were only able to resolve the image of pint-sized Philae because Rosetta’s decaying orbit brought it just 2.7 kilometers from the comet’s surface. In less than a month, Rosetta will end its 12-year mission with a crash landing of its own, and cease all communications with Earth. So finding Philae now, just before the fade to black, is a great piece of luck—for Philae’s fans, and for near-Earth asteroid science.
Now that scientists know Philae’s final position, they can put its impact data into context—and that could bring them closer to fielding a viable deep space mission. Mark McCaughrean, senior science advisor for ESA, calls it the comet’s “ground truth.” The ESA now knows the probe’s orientation, what materials it’s leaning against, and how much solar radiation it’s exposed to. It can also compare the specs of Philae’s location to the characteristics of the rest of the comet with much greater precision. “We were very interested in what Philae has told us about the comet’s mechanics,” says Daniel Faber, CEO of Deep Space Industries. “We now know it follows a crème brûlée model: The surface is crispy, but the interior is soft, and there’s not much to it.”
That’s exciting news. Knowing more about comet’s surface structure will allow engineers to design crafts better equipped to land on them, and hopefully avoid repeating Philae’s bumpy ride. And if landing gets easier and comets (and similarly-structured asteroids) are easily mineable, as comet 67P/Churyumov–Gerasimenko appears to be, they could act as a mobile supply stations for deep space missions. Space miners could break the ice down into hydrogen and oxygen for propellants or radiation shielding (or breathing). And they could convert comets’ rich supply of hydrocarbons into 3D-printed polymers to be used for … well, pretty much anything. That would solve some big space exploration headaches, from astronauts succumbing to radiation poisoning to exhausting fuel reserves (or fuel-purchasing funds) mid-mission.
And while Philae and Rosetta point to where humanity is headed, they’re also helping scientists piece together where it came from. “With the Earth, we’re looking at a finished cake on the counter in front of us,” says McCaughrean. “Now we’ve got to open the cupboard, see what ingredients we have, and reverse engineer it to get the right taste.” The theory goes that comets are either the Big Bang’s shrapnel, or something even older and more interstellar—in either case, they’re icy time capsules. Comets may be the origin of Earth’s water supply, and the organic materials necessary for carbon-based life—the Rosetta mission found the amino acid glycine, a building block for proteins, on comet 67P/Churyumov–Gerasimenko. The comet where Philae and Rosetta will go to die is packed with clues about life.