Asteroid Westa can be a piece of lost planet, scientists say

Asteroid Westa, which has long been considered a stald protoplanet, can actually be a large piece of world that was once present in our solar system. New conclusions based on gravity-field mapping and spin-rate data suggest that Westa lacks dense core that are commonly found in differential planetary bodies. The search challenges the previous beliefs drawn from NASA’s Don Mission in 2012, which classified Westa as a fetal planet. Now, scientists reported that Westa was thrown out of a differential world in large -scale confrontation 4.5 billion years ago, which enhances ideas about the development of planets and asteroids.

New gravitational data shows that Westa is a wreckage from a destroyed planet, not a protoplanet

According to a new Study On April 23, 2025 published in Nature Astronomy, Westa does not coincide considerably with the former model. Refined calibration methods confirmed the absence of a metal-rich core, polishing the radio Doppler signals, which was incompatible with earlier work. Seth Jacobson of Michigan State University, who led the research, said the new interpretation has made a major change in planetary science. While the basaltic, volcanic surface of Westa still indicates geological activity, its internal uniformity refutes the expectations of a body that goes through complete discrimination once.

This contradiction has caused scientists to reconsider the heritage of asteroid. A scenario is that Westa started differences but never far away. But the figures of meteorites are called Howardite-Ekrite-Dygenites (HEDs), thought that came from Westa, showing no signs of such incomplete discrimination. Jacobson and his team instead favor the clarification that Westa was separated from a fully developed planet during an ancient planetary confrontation, which could also portray its volcanic surface without the need of a dense core.

The results not only question Westa’s identity, but also suggest the possibility of a more general principle: other asteroids may also be pieces of broken planets. NASA’s Manas and ESA’s Hera Mission, planned for the next decades, intended to conduct such gravity check, which can eventually confirm this new approach. Jacobson said that Westa’s composition can also indicate in a shared origin with Earth or other early planets, a hypothesis that can reopen the asteroid science completely.