Thursday, November 13, 2014

ESA’s Philae lander successfully touches down on a comet, but harpoons have failed

The European Space Agency (ESA) has spent more than a decade planning for today, and it seems to have gone well. After traveling millions of miles through the solar system and slingshotting around a few planets, the Rosetta mission has successfully landed a probe on comet 67P/Churyumov-Gerasimenko at 11 AM ET (4 PM GMT). The live stream of the ESA control center showed mission managers celebrating several minutes later when the signal from Philae was confirmed on the surface.

The Philae lander was released from the main spacecraft seven hours before touchdown, which was itself a big deal. This mechanism had to be carefully designed to keep Philae secure for ten years until the big moment. It would have been a real bummer to travel all that way and not get to actually land because of a mechanical failure. After the trip down toward the surface, ESA mission control fired special harpoons from Philae to reel it in to the surface–or rather, that was the plan. 67P is a few miles across, so it’s not exactly small, but its gravity is low enough that Philae needs a little stabilizing. According to the Philae Twitter account, the harpoons have not deployed correctly. This probably isn’t a huge deal yet, but the team is working on a fix.

The landing took place at Site J, later renamed Agilkia to fit with the mission’s Egyptian naming scheme. This location was chosen from a list of possibilities due to its even terrain and good accessibility on the smaller of 67P’s two lobes.


Of course, landing the probe is only the first step in gathering useful data. Mission control verified that all of Philae’s communication systems were working after touchdown, which ensures it will be able to get its findings back to Earth. While on the surface, Philae will take photos and drill into the nucleus of 67P to analyze its composition with an array of 16 instruments, three of which come from NASA.

The only other direct contact humanity has had with a comet was the NASA Deep Impact mission. That contact was a bit more violent than Philae’s gentle touchdown. The Deep Impact probe smashed into the comet to kick up a cloud of dust for analysis. Getting a functional probe on the surface of 67P allows scientists to watch as the comet forms a coma of dust and gas during its trip through the inner solar system.

Scientists believe comets like 67P/Churyumov–Gerasimenko contain the primitive building blocks of the solar system, left virtually untouched for billions of years. Rosetta and the now-independent Philae will study the comet up close. The active phase of the mission is expected to last through mid-2015 when 67P will be heading back out into the cool depths of the outer solar system until its return in about six years.


We’re still waiting to see the first images from the surface of 67P, but you can follow the Philae lander’s bizarrely anthropomorphized account on Twitter, where images will probably be posted as soon as they’re available. Right now mission control is busy working on the harpoon problem, so this is still something to keep an eye on.

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