Peanut or Asteroid?

4179 Toutis, from NASA

According to Space.com, a 3-mile wide asteroid, 4179 Toutatis, is approaching within 4.3 million miles of Earth tonight. It's one of many Earth-crossing asteroids whose orbits cross the Earth's path. At about 17 times the distance to the moon, this "close" approach is not so close, but some of these Earth-crossing asteroids can swing in closer than the moon. With current technology it's quite possible to send a manned mission to an Earth-crossing asteroid. In Beyond Earth Chapter 3, "The Face of Icarus," we join a European manned space mission to an Earth-crossing asteroid, and there they find more than they bargained for.

What's interesting about the asteroid above and many others is its peanut shape. Asteroids commonly have small moons orbiting them, or they appear to have merged with their moons to form bumpy peanut shapes. The more scientists study asteroids, the more they find them to be floating rock piles held together by water ice. Sounds a lot like a comet, doesn't it? It appears that asteroids and comets have one and the same origin, involving water in a liquid or gaseous state.