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Ancient Asteroid Impacts Left Serpentine Traces On Vesta: Study

Mosaic synthesizes some of the best views the spacecraft had of the giant asteroid Vesta. Dawn studied Vesta. 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. Credit: NASA/JPL-Caltech/UCAL/MPS/DLR/IDA

Mosaic synthesizes some of the best views the spacecraft had of the giant asteroid Vesta. Dawn studied Vesta. 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. Credit: NASA/JPL-Caltech/UCAL/MPS/DLR/IDA

While “dark materials” may leave some of us thinking about a certain Philip Pullman book series, on the asteroid Vesta its presence belies something equally exotic: old smaller asteroid impacts on its surface.

The dark stuff on the lighter surface has puzzled researchers since it was discovered in 2011 (and has been brought up in other studies), but a new team says it has found that serpentine is among the components.  Because that mineral can’t survive temperatures that are more than 400 degrees Celsius (752 degrees Fahrenheit), this means that scenarios such as volcanic eruptions can’t have caused it. This leaves only smaller asteroids, the team says.

“These meteorites are regarded as fragments of carbon-rich asteroids. The impacts must have been comparatively slow, because an asteroid crashing at high speeds would have produced temperatures too high to sustain serpentine,” the Max Planck Institute for Solar System Research stated.

Image of the crater Numisia on Vesta, where researchers found the spectral signature of serpentine. Picture taken by NASA's Dawn spacecraft. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Image of the crater Numisia on Vesta, where researchers found the spectral signature of serpentine. Picture taken by NASA’s Dawn spacecraft. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

 

“In a previous study, scientists from the MPS had calculated how dark material would be distributed on Vesta as a result of a low-speed oblique impact. Their results are consistent with the distribution of dark material on the edge of one of the two large impact basins in the southern hemisphere.”

The results came from analyzing images the NASA Dawn spacecraft took of Vesta between July 2011 and September 2012. The researchers recalibrated the data and also backed up their results by examining serpentine in laboratory conditions.

The research was published in the journal Icarus and you can also read a summary of the research here, from a presentation at the 2014 Lunar and Planetary Science Conference.

Source: Max Planck Institute for Solar System Research

About 

Elizabeth Howell is the senior writer at Universe Today. She also works for Space.com, Space Exploration Network, the NASA Lunar Science Institute, NASA Astrobiology Magazine and LiveScience, among others. Career highlights include watching three shuttle launches, and going on a two-week simulated Mars expedition in rural Utah. You can follow her on Twitter @howellspace or contact her at her website.

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