Escape velocity
Escape velocity is the speed an object needs to break free of a body's gravity without further push.
Escape velocity is the minimum speed something must reach to leave a planet, moon or asteroid for good, ignoring air resistance. It depends on the body's mass and size. For Earth it is about 11.2 kilometres per second. For Mars it is about 5.0, for the Moon about 2.4 and for Vesta only about 0.36 kilometres per second.
Escape velocity explains why some bodies send us meteorites more easily than others. Impacts on the Moon and Mars can launch rocks faster than escape velocity, so we have lunar and Martian meteorites. Venus and Earth have much higher escape velocities and thick atmospheres, so it is extremely hard for rock to be blasted off them.
It also sets a minimum speed for meteors. Anything falling to Earth from space must arrive at least at Earth's escape velocity, about 11 kilometres per second, because it gains that speed falling into Earth's gravity. That is the lower limit of meteor speeds.
Related terms
Level: Explorer Ages 10 and up