\n<\/p>\n
Your support = more science, more stars, more wonder.<\/strong> Vesta is a rocky world orbiting the sun in the asteroid belt. In fact, it contains about 9% of the mass of the entire asteroid belt. And it\u2019s the brightest member of the asteroid belt. Yet it\u2019s not technically an asteroid. But neither is it a planet. Astronomers once thought it was a world with a core, mantle and crust that just didn\u2019t fully reach planet status. But on April 28, 2025, a team of researchers said Vesta doesn\u2019t have a core. So what is<\/em> Vesta?<\/p>\n A re-analysis of NASA Dawn mission data led to the discovery Vesta has no core. The team of scientists said there are two possible explanations for how Vesta came to be. First, it might never have completed the process of differentiation, where dense metals sink to the core. Or second, it might be a broken fragment of a planet that was forming in the early solar system.<\/p>\n The researchers published their peer-reviewed study in the journal Nature Astronomy<\/em> on April 23, 2025.<\/p>\n So why did astronomers think Vesta had a core? The outer surface of Vesta consists of volcanic basaltic rocks. That\u2019s different from what astronomers see in other asteroids, which have surfaces of ancient stony gravel. The volcanic basaltic rocks made scientists think the world had undergone the hot, melting process of differentiation, sending the heavier elements to the core.<\/p>\n The Dawn mission to Vesta ended in 2012. But better processing of the Dawn data through the years revealed new insights. Lead author Ryan Park of JPL said: <\/p>\n For years, conflicting gravity data from Dawn\u2019s observations of Vesta created puzzles. After nearly a decade of refining our calibration and processing techniques, we achieved remarkable alignment between Dawn\u2019s Deep Space Network radiometric data and onboard imaging data. We were thrilled to confirm the data\u2019s strength in revealing Vesta\u2019s deep interior. Our findings show Vesta\u2019s history is far more complex than previously believed, shaped by unique processes like interrupted planetary differentiation and late-stage collisions.<\/p>\n<\/blockquote>\n When the team took another look at the measurements for Vesta\u2019s rotation and gravity field, they realized Vesta didn\u2019t behave like an object with a core.<\/p>\n Researchers just don\u2019t know yet. But scientists have studied meteorites on Earth that came from Vesta. And those meteorites lean away from the incomplete differentiation scenario. Co-author Seth Jacobson of Michigan State University said: <\/p>\n We\u2019re really confident these meteorites came from Vesta. And these don\u2019t show obvious evidence of incomplete differentiation.<\/p>\n<\/blockquote>\n So what about the fragment theory? In the early days of the solar system, objects would have been bashing into each other and fragmenting. If this happened to Vesta, the resulting debris would include melted rocks without evidence of a core. <\/p>\n Jacobson had already been working with the idea that some main belt asteroids are fragments of planets. But he said they\u2019ll need to do more modeling to determine if Vesta really is a former chunk of a young planet. And perhaps Vesta is even a piece of home. Jacobson said: <\/p>\n No longer is the Vesta meteorite collection a sample of a body in space that failed to make it as a planet. These could be pieces of an ancient planet before it grew to full completion. We just don\u2019t know which planet that is yet.<\/p>\n<\/blockquote>\n Bottom line: What is Vesta? It\u2019s neither an asteroid nor a planet. And a new study shows Vesta doesn\u2019t have a core, which could lead to two possibilities for how it formed.<\/p>\n Source: A small core in Vesta inferred from Dawn\u2019s observations<\/p>\n Via Michigan State University<\/p>\n <\/div>\n
Donate to EarthSky and be part of something bigger.<\/p>\nWhat is Vesta?<\/h3>\n
No core for Vesta after all<\/h3>\n
\n
So which hypothesis is correct?<\/h3>\n
\n
\n