This is the picture of Vesta, which is an object in our solar system:
That’s the picture that Wikipedia uses as of this writing, and it was taken by the Hubble. The key thing to note is that Vesta, which lies in the asteroid belt and has been thought of as a big asteroid, is very globular like a planet. This is unusual for an asteroid.
This is a picture of Vesta as conceptualized by NASA scientists. It is a model, not a photograph.
The images incorporate the best data on dimples and bulges of the protoplanet Vesta from ground-based telescopes and NASA’s Hubble Space Telescope. The cratering and small-scale surface variations are computer-generated, based on the patterns seen on the Earth’s moon, an inner solar system object with a surface appearance that may be similar to Vesta.
Vesta makes up about 9% of the entire asteroid belt. In fact, if you take the largest handful of objects in the asteroid belt, Ceres (that’s the largest), Vesta, Pallas and 10 Hygiea, you’ve got half of the mass of the entire thing, according to the most current estimates. This sort of thing makes one wonder if some or all of these objects should be thought of as something other than asteroids. And this is a question that has been raised in relation to NASA’s Dawn project.
“I don’t think Vesta should be called an asteroid,” said Tom McCord, a Dawn co-investigator based at the Bear Fight Institute, Winthrop, Wash. “Not only is Vesta so much larger, but it’s an evolved object, unlike most things we call asteroids.”
The layered structure of Vesta (core, mantle and crust) is the key trait that makes Vesta more like planets such as Earth, Venus and Mars than the other asteroids, McCord said. Like the planets, Vesta had sufficient radioactive material inside when it coalesced, releasing heat that melted rock and enabled lighter layers to float to the outside. Scientists call this process differentiation.
McCord and colleagues were the first to discover that Vesta was likely differentiated when special detectors on their telescopes in 1972 picked up the signature of basalt. That meant that the body had to have melted at one time.
Special sensors. I gotta get one of those.
Anyway, this July, the Dawn Space Robot will approach Vesta and spend about a year in the vicinity. We’ll see how close that model is, and hopefully, Wikipedia can get a better portrait of the protoplanet/minorplanet/asteroid!
More details on the project are here.