For decades, scientists have believed that Vesta, one of the largest objects in the Main Asteroid Belt, is not just an asteroid, but rather a protoplanet. However, the results of a new study by scientists from Michigan State University cast doubt on this claim.
Bigger than asteroid
With a diameter of 525 kilometers, Vesta is the second largest object in the asteroid belt after the dwarf planet Ceres. Between 2011 and 2012, it was studied by the Dawn spacecraft, which mapped its surface and also collected data that allowed us to assess its internal structure.
Most asteroids are composed of ancient cosmic sedimentary gravel. In contrast, the surface of Vesta is covered with volcanic rocks composed of basalt. These rocks indicate that Vesta went through a melting process called planetary differentiation, where metal moves down toward the center and forms the core. Thus, it should be a protoplanet, one of several hundred planetary embryos that existed in the solar system after its formation. Over hundreds of millions of years, they collided with each other, causing them to increase in size and decrease in number. Eventually, there were only a few planet embryos left that merged into full-fledged planets. Somehow, Vesta escaped the collision and reached our days relatively intact as a kind of relic from that era.
However, a new, more detailed analysis of gravity data collected by the Dawn mission casts doubt on this claim. Planetary scientists can estimate the size of a celestial body’s core by measuring the so-called moment of inertia. Celestial bodies with a dense core move differently than bodies without a core. Armed with this knowledge, the research team measured Vesta’s rotation and gravitational field. The results indicate that Vesta does not behave like an object with a core, which disproved previous ideas about its formation.
Two hypotheses
Researchers have two hypotheses to explain the unusual nature of Vesta. According to the first, it went through incomplete differentiation. That is, Vesta began the melting process necessary to form separate layers such as the core, mantle, and crust, but for some reason never completed it.
The second hypothesis is even more intriguing. It suggests that Vesta is a huge fragment that broke off from a planet that formed at the dawn of the solar system. This explains the presence of fusion rocks on its surface and the absence of a core. The main question is which planet it was and whether it exists now.
According to the words of scientists, both hypotheses have their own strengths and weaknesses that require additional research to explain. But in any case, they have the potential to forever change existing ideas about the nature of Vesta.
According to Phys.org
