On Nov. 12, 2014, 317 million miles (510 million kilometers) from Earth and 14 miles (22.5 km) from comet 67p, the European Space Agency's Rosetta probe releases the Philae lander.
Full Story: Surprising Comet Discoveries by Rosetta's Philae Lander Unveiled
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A comet nucleus has very low gravity, so the lander relied on harpoons, hold-down thrusters and ice screws to secure itself to the surface. When these mechanisms all failed, the lander bounced back into space for a 1 hour and 50 minute ballistic flight. Due to Comet 67P's low gravity, Philae weighed about the same as a paper clip. On its first rebound, Philae ascended with a speed of 15 inches (38 centimeters) per second. Escape velocity from the comet is 19.7 inches (50 cm) per second.
A grazing collision with rim of crater Hatmehit caused Philae to begin tumbling. The lander's second impact with the comet was followed by about 7 more minutes of drifting.
The closest view taken by Philae, just before its first impact, reveals a granular soil called regolith, littered with blocks up to 16.4 feet (5 meters) in size. Scientists estimate the regolith to be between zero and 6.4 feet (2 m) deep.
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