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KNOXVILLE — Researchers at the University of Tennessee are playing a key role in a NASA mission set to launch this week to explore two of the largest asteroids in the solar system and provide information that will help us understand the early stages of Earth.

The mission, called DAWN, will send an unmanned spacecraft first to the asteroid Vesta, and then on to the more distant asteroid Ceres. The spacecraft will stop at each asteroid, orbiting and mapping the surface with a number of instruments designed to help scientists understand what the asteroids are made of and gain insight into how they were formed.

“These asteroids are some of the largest in existence, and they have a great deal to teach us about how planets like Earth were formed billions of years ago,” said UT distinguished professor of earth and planetary sciences Hap McSween.

McSween is an expert on meteorites, and he has specifically studied rocks that have fallen to Earth that are believed to have come from Vesta. As the DAWN spacecraft sends back data, McSween and his team will compare that data to information collected from meteorites here on Earth. In doing so, they will be able to better interpret the information found by DAWN and develop a better understanding of the asteroids’ nature.

One interesting aspect of the DAWN mission is that it will use ion propulsion, a new method of propelling the spacecraft. Once in space, vehicles typically rely on rockets or gases to push them forward, an approach that requires them to carry more weight and limits how far they can travel.

Instead, DAWN will use a plasma generator to emit a stream of small particles that will slowly cause the spacecraft to build momentum. While it is not the fastest method of space travel, it reduces the craft’s weight and requires less energy, allowing it to travel for a longer period of time. It will take approximately four years for DAWN to travel the 1.9 billion miles to reach the first stop on its trip, Vesta.

Vesta is the third largest asteroid in the solar system at about 320 miles across — roughly the same width as the state of Tennessee. Scientists are especially interested in Vesta because of its unique shape. It has an enormous peak that formed as the result of an ancient collision. The peak and surrounding crater expose different layers of the rock, allowing for a more detailed comparison with the meteorites found on Earth.

“The key here is that these are the objects that Earth is made of,” said UT graduate student Rhiannon Mayne, one of the UT researchers working on the DAWN mission. Mayne studies eucrites, a type of meteorite from the volcanic remnants on Vesta’s crust. “Understanding these asteroids will help us put the Earth into context. It is easy to overlook the fact that these rocks are older than everything that has ever existed here on Earth.”

After DAWN departs Vesta, it will take another four-year journey, this time to Ceres, the largest asteroid in the solar system. According to McSween, Ceres is of special interest due to the possibility of water beneath the asteroid’s surface.

McSween and Mayne say they are excited to take part in a mission to study they may help reveal the origins of the meteorites that they have studied so extensively.

“Can we discover where these rocks originated? Can we delineate where they came from on the asteroid? It looks hopeful that we can,” Mayne said.

Other UT researchers taking part in the DAWN mission include postdoctoral researcher Tomo Usui, who is examining how to most effectively use the data collected by the instruments on DAWN, and graduate student Andrew Beck, who studies rocks that originated from deeper within the surface of Vesta.

More information on the DAWN mission is available online at http://www.nasa.gov/mission_pages/dawn/main/.


Jay Mayfield (865-974-9409, jay.mayfield@tennessee.edu)