10 Incredible Facts About The Philae Comet Landing

4. A Landing Instrument Broke During The Descent

Because the comet's gravity is relatively weak due to its small size, the lander had to make use of ice screws on its legs, along with two harpoons in order to prevent itself from drifting away. While the ice screws could potentially be used multiple times, the harpoons were one use only. During the descent, one of the thrusters on the lander failed. Intended to fire up after the lander touched the surface of the comet, to stop it from bouncing away when the harpoons were shot. This meant that the location of the lander's descent was of utmost importance, as there was absolutely no chance of a change of course. If the surface below the lander's descent had been unsuitable, it would have spelled disaster for the mission.