It's over. After orbiting the duck-shaped comet 67P/Churyumov–Gerasimenko for 786 days, the Rosetta spacecraft has landed softly on its surface and turned off its instruments for good. The touchdown was confirmed at 7:20AM ET as the last signals from the probe were received at the European Space Agency's mission control.
"I can announce full descent and I declare, hereby, that the mission has ended for Rosetta," said ESA mission manager Patrick Martin moments after signal ended. "The Rosetta mission was inspiring to many. Historic and pioneering, and it revolutionized how we understand comets and the Solar System. Farewell Rosetta, you've done the job that was space science at its best."
Rosetta went down swinging, sending back images and data all the way on its slow descent. The spacecraft hit the comet at speeds of around 2 miles per hour — a slow walking pace. This, combined with 67P's very weak gravity, meant it was a low-energy impact. However, Rosetta was never designed for a landing at all, and it was enough to render the craft inoperative.
This "grand finale," as the ESA called it, meant Rosetta could go out in style. Comet 67P is headed toward Jupiter, away from the Sun, and the spacecraft's solar arrays were always going to run out of power. By landing on the surface scientists were able to grab more information on a peculiarity of comet geography — meter-sized goosebumps known as "positive relief features." These are thought to be some of the original icy boulders that formed the comet some 4 billion years ago, and as such, are as old as the Solar System itself.
Project scientist Matt Taylor compared it to a rock band retiring before the lead singer's voice wears out. "That is what we are doing here with Rosetta," he told The Guardian. "It is maximizing what we can do with the spacecraft at this time. This plunge is the only way to get this science."
While Rosetta is no longer transmitting data back to Earth, scientists say there will be "decades" more work to do on the information it's collected. Rosetta measured 67P's water vapor, its magnetic field, and found organic compounds and chemicals in its structure. This last discovery gives some credence to theory that comets might have seeded life on Earth — perhaps plunging into the surface of the planet when it was little more than molten rock.
Perhaps the most surprising aspect of the mission has been the insights into comet structures. It had been thought that these celestial wanderers, which drift in, out, and around solar systems, were hard balls of rock and ice. Rosetta's observations, though, showed that 67P is actually porous and full of holes — 70 percent of the comet is empty space. Scientists compared the composition to spun sugar and cotton candy; more fluff than solid.
The exact fate of Rosetta, though, will never be known. It's possible it bounced a little on the surface of the comet, but there is no way of confirming this — no telescope on Earth is powerful enough to see its final resting place. You can see a mosaic of images from its descent below: