A geriatric non-planet, non-asteroid...thing... 04.04.11

Vesta was discovered on March 29, 1807 by German astronomer Heinrich Wilhelm Olbers. To call Vesta an asteroid is not entirely correct, but it is not exactly a planet either. Too small to even be considered a dwarf planet, it has layers that scientists discovered in 1972 had melted at some point, so it does meet some criteria of being a planet like Mars, Earth, or Venus. Or, at least, a “proto-” or “minor” planet (not quite a planet, like a planet that failed to develop all the way). And, it is tiny.


 Not that tiny, though. It is too large to be an asteroid. Most asteroids are usually only about 60 miles or less across; Vesta is about 330 miles across. Pieces of Vesta (called Vestoids) also orbit with the other asteroids and have reached Earth as meteorites.


In July, NASA’s Dawn mission should arrive to orbit the object for one year, and conduct dozens of experiments in the process. The theory from most astronomers is that Vesta is an object left over from the formation of our solar system, an object that missed out on its chance to join with other bits of rock and dust to form a larger planet. That being the case, astronomers are very excited about the prospect of studying the object with, possibly, the oldest dirt samples. The studies will begin by taking pictures of a massive crater at Vesta’s south pole, and then will orbit northward to study its terrain, surface composition, texture, topography, and gravitational field. The image here is an artistic rendering of how astronomers expect it to appear.

Image credit: NASA JPL.

Credit: NASA JPL.