The European Space Agency's Rosetta spacecraft has spent the past decade chasing the 2.5-mile-wide comet known as 67P/Churyumov–Gerasimenko, and today, it should finally succeed in landing a probe on it.
If successful, this will be the first time a human-made object has landed on a comet. It will not, however, be the first time humanity has made contact with one, as in 2005 NASA slammed its Deep Impact probe into one.
The probe, which is called Philae, will take approximately 7 hours to make the trip from Rosetta to the comet's surface. Once there, it will use solar panels to power its instruments and send information about the conditions on the comet to Rosetta.
It will continue to do so, scientists estimate, until March of next year, when the surface of the comet will become too hot for the probe to function.
UPDATE: After some initial concerns about "bouncing," the Philae probe indicated that it has successfully landed on 67P/Churyumov–Gerasimenko and is sending data back to Rosetta to be relayed to Earth.
Watch the livestream of the landing below.