Vesta, the second largest asteroid in our Solar System, has not experienced full differentiation into a metallic core, silicate mantle and basaltic crust, according to a new analysis of data from NASA’s Dawn spacecraft.
NASA’s Dawn spacecraft studied Vesta from July 2011 to September 2012. The towering mountain at the south pole — more than twice the height of Mount Everest — is visible at the bottom of the image. The set of three craters known as the ‘snowman’ can be seen at the top left. Image credit: NASA / JPL-Caltech / UCLA / MPS / DLR / IDA.
Discovered by Heinrich Wilhelm Olbers on March 29, 1807, Vesta is the only main-belt asteroid visible to the unaided eye.
It rotates once in 5.34 hours, orbits the Sun in 3.63 years, and has an ellipsoidal shape with radial dimensions of 286 x 279 x 223 km.
Due to its large size, Vesta has been believed to be a differentiated body with a core and a mantle just like our own planet.
“What is Vesta’s true identity? We have two hypotheses that need further exploration,” said Dr. Seth Jacobson, a researcher at Michigan State University, and colleagues.
“The first possibility is Vesta went through incomplete differentiation, meaning it started the melting process needed to give the asteroid distinct layers, like a core, mantle and crust, but never finished.”
“The second is that Vesta is a broken chunk off a growing planet in our Solar System.”
“For years, conflicting gravity data from Dawn’s observations of Vesta created puzzles,” said Dr. Ryan Park, a senior research scientist and principal engineer at NASA’s Jet Propulsion Laboratory.
“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.”
“We were thrilled to confirm the data’s strength in revealing Vesta’s deep interior.”
“Our findings show Vesta’s history is far more complex than previously believed, shaped by unique processes like interrupted planetary differentation and late-stage collisions.”
Celestial bodies with a dense core move differently than one with no core at all.
Armed with this knowledge, the researchers measured the rotation and gravity field of Vesta.
The results showed Vesta didn’t behave like an object with a core, challenging prior ideas about how it formed.
“More models need to be created and fine-tuned to prove that Vesta is an ancient chunk of a forming planet,” Dr. Jacobson said.
“Scientists can adjust how they study Vesta meteorites to dive deeper into either hypothesis.”
“They could also do further studies with the new approaches to the Dawn mission data.”
“Our paper is only the beginning of a new direction of study. It could forever change how scientists look at differentiated worlds.”
The paper was published in the journal Nature Astronomy.
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R.S. Park et al. A small core in Vesta inferred from Dawn’s observations. Nat Astron, published online April 23, 2025; doi: 10.1038/s41550-025-02533-7
