The European Space Agency's Rosetta mission is set to make history's first soft landing on the nucleus of a comet. To do it, Rosetta will release the Philae lander on Nov. 12, 2014 for its rendezvous with the Comet 67P/Churyumov-Gerasimenko, or 67P. Watch the landing live here.
Comet 67P's 2.5-mile-wide (4 kilometers) nucleus tumbles through space, completing a rotation in about 12.4 hours. This mountain of ice weighs about 11 billion tons (10 trillion kilograms). [See comet photos from the Rosetta spacecraft]
The comet has negligible surface gravity, so Philae must actively work to secure itself to the ground to avoid drifting away. At the moment of touchdown, the probe’s tripod landing gear absorbs the impact. Then several actions occur at once:
- Ice screws in each footpad immediately begin drilling on contact.
- Upward-firing thruster ignites to counter the recoil caused by the launch of the harpoons.
- Harpoons shoot into the ground and lines retract to pull the probe down to the surface.
The Philae lander is named after the island where an obelisk used to decode Egyptian hieroglyphs was found. Its Rosetta spacecraft was named for the Rosetta Stone, which helped scientists decipher Egyptian hieroglyphs.