What is escape velocity?
Escape velocity is the speed that an object needs to be traveling to break free of a planet or moon's gravity well and leave it without further propulsion. For example, a spacecraft leaving the surface of Earth needs to be going 7 miles per second, or nearly 25,000 miles per hour to leave without falling back to the surface or falling into orbit.
A Delta II rocket blasting off. A large amount of energy is needed to achieve escape velocity. Photo from Jet Propulsion Laboratory's Planetary Missions & Instruments image gallery http://www-b.jpl.nasa.gov/pictures/browse/pmi.html
Since escape velocity depends on the mass of the planet or moon that a spacecraft is blasting off of, a spacecraft leaving the moon's surface could go slower than one blasting off of the Earth, because the moon has less gravity than the Earth. On the other hand, the escape velocity for Jupiter would be many times that of Earth's because Jupiter is so huge and has so much gravity.
| Body | Mass | Escape Velocity in Kilometers/ Second | Escape Velocity in Miles/Hour |
| Ceres (largest asteroid in the asteroid belt) | 1,170,000,000,000,000,000 kg | .64 km/sec | 1430.78 mph |
| The Moon | 73,600,000,000,000,000,000 kg | 2.38 km/sec | 5320.73 mph |
| Earth | 5,980,000,000,000,000,000,000 kg | 11.2 km/sec | 25038.72 mph |
| Jupiter | 715,000,000,000,000,000,000,000,000 kg | 59.5 km/sec | 133018.2 mph |
| Sun | 1,990,000,000,000,000,000,000,000,000 kg | 618. km/sec | 1381600.8 mph |
| Sirius B (a white dwarf star) | 2,000,000,000,000,000,000,000,000,000 kg | 5,200. km/sec | 11625120 mph |