Rosetta's comet-harpooning lander is on its way down

A spacecraft harpooning a comet: it should be something out of a science fiction movie, but it's actually a mission underway right now, with the European Space Agency's Rosetta probe set to grapple with a chunk of hurtling space rock. The mission officially began back in 2004 when Rosetta and the Philae lander started their journey to comet 67P/Churyumov-Gerasimenk, but cranked up the excitement in the early hours of this morning as spacecraft and rock came together. Philae shared a last-minute photo on Twitter – which you can see after the cut, as well as live video of the action itself – and then began its careful journey down fourteen miles to the surface.

Comet 67P's own gravitational pull will help bring Philae and its contingent of instruments down, but it's up to the lander itself to keep itself situated once it's there. When you're talking about a rock with 100,000x less gravitational strength than you'd experience on Earth, that's not an easy matter.

So, the ESA has equipped Philae with two harpoons to spear the comet, along with shock-absorbing landing gear. Each of the three feet has a drill, to burrow into the crust, and finally there's an upward-facing rocket which can be used to pin the lander down by force.

Separation was completed at 08:35 GMT, though since it takes just short of a half hour for signals to travel between Rosetta and Earth, the ESA only knew it had happened a little while later.

Rosetta works as a relay station between Philae and the ESA, with data expected to include readings during the seven hour descent and photos of the point of contact.

The landing itself is expected to be confirmed in a one-hour window around 16:02 GMT, with the first photos around two hours later.

Among the reports are expected to be gas measurements and magnetic field measurements, as well as data on the properties of the surface. Philae will also have close-up images of the rock, together with feedback on the harpoon's success – or otherwise – too.

The results are expected to give new insights into the early formation of the Solar System, and the gas and dust clouds around 5 billion years ago. Rosetta traveled in total around 3.98 million miles.