Landing on a Comet: Philae Makes History

Land safely on a comet so far away that it takes half an hour for light and radio waves to travel back to Earth, making real-time control of the descent and landing impossible? On a comet hurtling through space at 64,800 kilometres per hour? On a comet where the gravity is so low that the spacecraft bounced before finally coming to rest? And did we mention: land on a comet?

Well, the European Space Agency just did all of that, reporting on Thursday that the Philae lander had become the first spacecraft in human history to land on a comet, touching down on the icy, irregulalry shaped, 67P/Churyumov-Gerasimenko at about 1500 GMT.

Now, not everything happened as smoothly as planned: the time-delay between Earth and comet 67P meant that the entire landing sequence had to be preprogrammed and set up in advance, leaving mission control with very little opportunity to respond if anything went wrong. On the weak gravity of the comet, the Philae lander’s harpoon system (designed to anchor it securely to the comet) failed to work, and the lander bounced twice before coming to rest about a kilometre from the targeted landing area. Unfortunately, this new landing spot is not in direct sunlight, meaning that the lander’s rechargeable batteries have so far been unable to charge.

Nevertheless, scientists at the ESA were able to conduct tests and experiments on the comet’s surface for about sixty hours, and all of the data was transmitted back to Earth before the lander went into temporary hiberation. The lander’s mother-ship, Rosetta, continues to orbit the comet, collecting photographs and data, and researchers are hopefully that they will be able to power up the lander again as the comet hurtles closer to the sun.