Solar System Gravity Wells

On Monday (December 28), Randall Munroe released an XKCD comic on gravity wells. It's a funny, but accurate, way to look at and compare the sizes and masses of the bodies in the solar system. So what exactly is a gravity well?

Gravity wells are just a handy way to display the gravitational potential field around an object. The comic shows gravity wells for the planets and other bodies in the solar system. If these wells existed on the Earth, with constant Earth surface gravity, it would take the same amount of energy to escape from the well as it would to escape from the planet's gravity in reality. So, as the comic shows, to escape from Deimos, one of the moons of Mars, you would just need a bike and a ramp, just as if you had to climb out of a well almost as tall as you (about 1.62 meters or 5.53 feet).

I also found it interesting that Randall Munroe decided to show the planets' sizes as well when drawing the gravity wells. It effectively shows Jupiter's greater density than Saturn.

Be sure to explore the entire comic by clicking it above to view a larger image. There's a lot of great things hidden in the comic (like an explanation of the differences in rocket size of the Apollo missions, a "Your mom" joke between Jupiter and Saturn, and Carl Sagan on Neptune).

Comic: Randall Munroe, XKCD

Astronomy and Space Celebrates International Year of Astronomy 2009.