Visualisation of the deployment of the Philae lander from Rosetta at comet 67P/Churyumov-Gerasimenko in November 2014. Rosetta will come to within 2.5 km of the comet’s surface to deploy Philae, which will then take around 2 hours to reach the surface. Because of the comet’s extremely low gravity, a landing gear will absorb the small forces occurring during landing while ice screws in the probe’s feet and a harpoon system will lock the probe to the surface. At the same time a thruster on top of the lander will push it down to counteract the impulse of the harpoon imparted in the opposite direction. Once it is anchored to the comet, the lander will begin its primary science mission, based on its 64-hour initial battery lifetime. Then it will use solar cells to recharge and attempt to operate for several further weeks to months, depending on the activity of the comet and how quickly the solar cells are covered in dust.