The ticker at the top of the European Space Agency's live stream says it all. Days at comet: 786; days until end of mission: 0. After launching from Earth back in March 2004, the Rosetta space probe is preparing for its final mission — a controlled landing onto the surface of comet 67P/Churyumov–Gerasimenko, where it's been in orbit for the last two years. Confirmation from Rosetta of the landing is expected to happen at approximately 11:18AM Universal Time or 7:18AM ET, and you can watch along with the ESA's live stream.
If you're tuning in at the time of publication article (4:30AM ET) then don't expect to see more than a quiet control room. But as we get closer to impact, Rosetta will be sending more images back to Earth, charting its own final plunge with good, scientific rigor. This will be a relatively soft landing, with Rosetta hitting the surface at a leisurely pace of around 2 mph, but it'll be enough to render the craft inoperative.
The landing is optional, too. "We could have abandoned it in space or let it bounce off the comet and just switched it off. It wouldn’t have created any problem," Andrea Accomazzo, Rosetta flight operations director, told The Guardian. "Landing it is more a psychological thing." Rosetta is expected to transmit a last image of the comet's surface from a height of around 15 meters. After this, scientists will turn off its radio transmitters and the probe will be gone for good.
Rosetta's scientific legacy, though, is already secured. Scientists have used information collected by the probe to confirm that comets like 67P are the frozen remains of the material used to build planets. And while measurements of 67P's very weird water vapor suggest that that theory that comets seeded planets with water is false, the discovery of numerous organic compounds and chemicals by Rosetta suggest that it's possible that comets sparked life on Earth, crashing into the primordial soup.