Dawn Reveals Asteroid Vesta's Internal Structure, Reshaping Planet Formation Theory

Scientists are learning a little bit more about the asteroid, Vesta, and its internal structure. With the help of numerical simulations and data from the space mission Dawn, researchers have taken a closer look at its internal structure.

The asteroid Vest is actually one of the largest known planet "embryos." It has a diameter of 500 kilometers, and first came into existence around the same time as the solar system. That's why NASA sent the Dawn spacecraft into Vesta's orbit for one year.

With the help of the data collected by Dawn, the researchers found that the asteroid's crust is almost three times thicker than expected. This has implications for the structure of the asteroid, which is located between Mars and Jupiter. Not only that, but the findings change a fundamental component in planet formation models; more specifically, it changes the composition of the original cloud of matter that aggregated together, heated, melted and then crystallized for form planets.

So how did they come to this conclusion? It all had to do with the asteroid's composition on the surface.

"What is striking is the absence of a particular mineral, olivine, on the asteroid's surface," said Philippe Gillet, one of the researchers, in a news release.

Olivine is the main component of planetary mantles and should have been found in large quantities on the surface of Vesta. Scientists thought that a double meteorite impact that hit Vesta would have "dug" the asteroid's southern pole to a depth of 80 km and catapulted large materials to the surface. But apparently these impacts weren't strong enough to pierce through the curst to reach the asteroid's mantle. This means that the asteroid's crust was far thicker.

So how does this have implications for Vesta's formation? The researchers believe that in contrast to previous theories, it's likely that Vesta's crust was thickened by the formation of "plutons," which are igneous rock intrusions, some of which emerged to the surface. This, in turn, has implications for how planets like Earth formed.

The findings are published in the journal Nature.