July 18, 2014
Investigations Of Asteroid Vesta Have Scientists Rethinking Theories Of Planet Formation
Brett Smith for redOrbit.com - Your Universe Online
An investigation of Vesta, a massive asteroid that orbits the Sun between Mars and Jupiter, has revealed that the planet-like body has a thicker crust than previously thought, which calls into question the internal structures of other planets in the Solar System.
The investigation, which is published in the journal Nature, is based on data from the Dawn spacecraft that NASA sent into Vesta's orbit between July 2011 and July 2012. Using mathematical models based on Dawn’s data, the study team found Vesta’s crust is three times thicker than previously thought.
The asteroid is thought to have experienced two major impacts in its existence. Study author Harold Clenet points out a particularly interesting detail about the composition of the rocks strewn across Vesta's ground as a result of those impacts. "What is striking is the absence of a particular mineral, olivine, on the asteroid's surface," said Clenet, a postdoctoral researcher at the Ecole Polytechnique Fédérale de Lausanne in Switzerland.
[ Watch the Video: Asteroid Vesta To Reshape Theories Of Planet Formation ]
Olivine is a green mineral common to Earth’s mantle and thought to be common in the interiors of all the planets in the Solar System. Based on a series of mathematical models, the study team said they expected to see large amounts of olivine excavated from Vesta’s interior by the impacts.
"But these cataclysms were not strong enough to pierce through the crust and reach the asteroid's mantle," Clenet said.
The two impacts on Vesta are thought to be so significant – 5 percent of all of Earth’s meteorites come from the asteroid. The meteorites coming from Vesta discovered on Earth validate a lack of olivine excavation since they commonly lack the mineral or consist of only small amounts – as opposed to the amounts seen in planetary mantles. The researchers pointed out that Dawn was unable to find olivine near the two impact craters.
"This means that the crust of the asteroid is not 30 km (19 miles) thick, as suggested by the models, but more than 80 km (49 miles)," Clenet said.
The study team said their findings call for a rethinking of models that describe the formation of Vesta, as well as the other planetary bodies in the Solar System.
"The crust might have been thickened by the formation of 'plutons,' that is: igneous rock intrusions, hundreds of meters large, some of which emerged to the surface,” Clenet said.
The study team believes a more complex planetary formation model should be worked towards that accounts for not only the original structure of planets, but also their orbits, dimensions and associated cooling periods. Vesta may very well be the only asteroid with an Earth-like composition making it an ideal laboratory for assessing hypotheses and theories, the researchers said.
Image 2 (below): This is an infographic of Asteroid Vesta. Credit: EPFL/Jamani Caillet