Scientists Map the Geologic History of Asteroid Vesta

It turns out that the asteroid Vesta may have a history of large impacts. Scientists have completed the first geological and tectonic map of the asteroid, revealing a bit more about its past.

The mapping itself was done with images from NASA's Dawn spacecraft, which orbited Vesta between June 2011 and September 2012. These images allowed scientists to create high-resolution geological maps, revealing the variety of Vesta's surface features in unprecedented detail.

"The geologic mapping campaign at Vesta took about two and a half years to complete," said David Williams, the lead researcher, in a news release. "The resulting maps enabled us to construct a geologic time scale of Vesta for comparison to other planets and moons."

It turns out that Vesta's geologic time scale has been shaped by a sequence of large impact events. The biggest of these events were the impacts that blasted the large Veneneia and Rheasilvia craters early in Vesta's history, and the Marcia crater late in its history.

Yet how long ago did these impacts actually occur? Figuring out age is difficult since samples from Vesta did not show a clear formation of age that can be linked to specific features on the asteroid.

"So figuring out an actual date in years is a step-by-step process," said Williams. "We work with rock samples from the moon, mostly from Apollo missions decades ago. These gave actual dates for large lunar impacts."

It turns out that the oldest surviving crust on Vesta predates the Veneneia impact, which occurred 2.1 billion years to 3.7 billion years ago. The Rheasilvia impact, in contrast, has an age of 1 billion to 3.5 billion years.

"Vesta's last big event, the Marcia impact, has an age that's still uncertain," said Williams. "But our current best estimates suggest an age between roughly 120 and 390 million years."

The findings reveal a bit more about Vesta and may actually tell scientists a bit more about the history of our solar system.