Capitol News

On April 28, 2025, research findings published in Nature Astronomy have challenged long-standing perspectives on Vesta, a massive object located in our solar system’s asteroid belt. Traditionally thought to be a protoplanet, the study suggests Vesta may not have the core previously believed to exist.

A Michigan State University (MSU) assistant professor, Seth Jacobson, played a key role as a co-author in the research team led by NASA's Jet Propulsion Lab (JPL). Jacobson expressed, “The lack of a core was very surprising. It’s a really different way of thinking about Vesta.”

The study proposes two hypotheses. The first suggests Vesta underwent incomplete differentiation—a process where distinct layers such as the core, mantle, and crust form through melting, which was left unfinished. The second hypothesis, initially proposed by Jacobson years ago at a conference, views Vesta as potentially a fragment from a growing planet, resulting from planetary collisions.

“This idea went from a somewhat silly suggestion to a hypothesis that we’re now taking seriously due to this re-analysis of NASA Dawn mission data,” Jacobson remarked.

NASA's Dawn mission, launched in 2007, had aimed to study Vesta and Ceres to unlock insights about planetary formation. Its data, gathered between 2011 and 2012, revealed new details after further analysis. Ryan Park, a JPL researcher, emphasized, “After nearly a decade of refining our calibration and processing techniques, we achieved remarkable alignment between Dawn’s Deep Space Network radiometric data and onboard imaging data.”

The research leverages the concept of the moment of inertia to investigate Vesta’s interior. Jacobson explained the process by likening it to the momentum changes of a spinning figure skater. The study surgically analyzed Vesta’s gravity field and rotation, finding no evidence of a core, thus questioning prior assumptions about its formation.

The dual hypotheses remain unresolved. While incomplete differentiation could explain Vesta’s composition, researchers like Jacobson are confident the meteorites collected do not indicate this scenario. The alternative idea of Vesta being debris from planet formation is still under exploration.

Jacobson, collaborating with his graduate student Emily Elizondo, continues to explore the remnants in the asteroid belt that might originate from formative planetary fragments. The new study advocates for more focused research on Vesta meteorites and further examination of Dawn mission data. Jacobson noted, “These could be pieces of an ancient planet before it grew to full completion. We just don’t know which planet that is yet.”