A recent study published in Nature Astronomy revives the debate about the origin of Vesta, one of the largest asteroids in the belt between Mars and Jupiter. Thanks to data from the
Dawn probe, which observed Vesta from 2011 to 2012, scientists have gained a better understanding of this celestial body, considered a witness to the earliest moments of the Solar System.
Vesta has a differentiated structure: in brown, the metallic core; in green, the rocky mantle; in gray, the crust.
Image Wikimedia An asteroid unlike any other
Vesta is covered with rocks formed very early, within the first few million years after the Sun's birth. This makes it a key object for studying the formation of the first planets. However, its internal structure remains poorly understood. To make progress, researchers attempted to estimate its
moment of inertia, a parameter that provides insights into the mass distribution inside. This calculation relied on variations in the radio signal sent by the Dawn probe, measured from Earth.
The new data indicate that Vesta does not have as clear-cut a structure as a planet, with only a weak separation between the crust, mantle, and a small core. In other words, it did not fully "melt" internally like other, larger celestial bodies.
Two possible origins
Researchers propose two hypotheses.
According to the first, Vesta may have formed a
bit too late, at a time when the internal heat source, a radioactive element called
26Al, had already partially migrated to the surface. This would have prevented the asteroid's interior from heating enough to fully differentiate.
In the second scenario, Vesta could have been
a fragment of a larger body, originally fully differentiated, but shattered by a giant collision before reforming into a smaller object.
These findings confirm that the formation of Solar System objects is far from simple. Factors such as the timing of formation, the distribution of internal heat, or collisions play a major role, and each asteroid tells a different story.