Scientists say asteroid ‘Vesta' might be a piece of a planet that no longer exists

Indian Express

19-05-2025

Asteroid Vesta, long considered to be a stalled protoplanet, may actually be just a fragment of a larger world that once existed in our solar system. New research suggests that Vesta may not have the dense core that differentiated planetary bodies usually have.
Due to spin-rate data and gravity-field mapping, a new study by Michigan State University researchers published on April 23, in Nature Astronomy, has challenged previous assumptions that gave Vesta with the status of an embryonic planet based on NASA's 2012 Dawn mission.
Instead, the study has suggested, Vesta may have been ejected from a different world in a massive collision that is estimated to have occurred 4.5 billion years ago.
Vesta does not exactly fit the model of a planet, as per the study. The radio Doppler signals were refined using enhanced calibration techniques, confirming the lack of a metal-rich core that had been disputed by previous research.
Seth Jacobson of Michigan State University, who led the research, stated that the new interpretation marks a major shift in planetary science. Although Vesta's volcanic, basaltic surface still shows signs of geological activity, its internal homogeneity defies what one might expect from a body that has undergone complete differentiation, Jacobson said.
This paradox has caused scientists to reconsider the asteroid'sheritage. Vesta started to differentiate but never made much progress. However, howardite-eucrite-diogenites (HEDs), which are meteorites thought to have formed in Vesta, lack any evidence of this kind of incomplete differentiation.
Instead, Jacobson and his team have claimed that their study supports the theory that Vesta was created by material that was blasted off of a fully formed planet during an ancient planetary collision. This theory might also explain Vesta's volcanic surface without requiring that it have a broad core, they said.
The study raises doubts about Vesta's identification and also raises the prospect of a wider theory that other asteroids might also potentially be fragments of broken planets. This viewpoint may eventually be confirmed by the gravity investigations planned for the upcoming decades by NASA's Psyche and ESA's Hera missions.
According to Jacobson, Vesta's makeup might even suggest that it shared an origin with Earth or other early planets, which might completely change the field of asteroid science.
Vesta is the second most massive body in the main asteroid belt, accounting for almost nine per cent of the total mass of all asteroids. In that area of rocky debris between Mars and Jupiter, the only dwarf planet larger than it is Ceres.
Vesta was discovered in Bremen, Germany, on March 29, 1807 by Heinrich Wilhelm Olbers. He had also discovered Pallas (a large asteroid, located in the asteroid belt between Mars and Jupiter). He believed, wrongly, that Ceres and Pallas were pieces of a destroyed planet and found Vesta while looking for more evidence. It was the fourth asteroid ever discovered.
Upon discovery, Olbers let German mathematician Carl Friedrich Gauss name the asteroid. Gauss named the celestial body 'Vesta' after the Roman goddess of the hearth and home.
From July 16, 2011 to September 5, 2012, NASA's Dawn spacecraft circled Vesta before leaving and beginning its mission to the dwarf planet Ceres. The giant asteroid is almost spherical, and was nearly classified as a dwarf planet.
Unlike the majority of known asteroids, Vesta is differentiated. This means that it has separated into a core, mantle, and crust. The brightness range of Vesta is among the widest of any solid body in our solar system. While the black material is believed to have been material left behind by previous asteroids that crashed into Vesta, the light materials seem to be native rocks.
(This article has been curated by Disha Gupta, who is an intern with the Indian Express)