A UT geology professor is working with NASA and other scientists worldwide on an eight-year project that could link two asteroids in space with conditions on Earth in its early years of formation. 

Hap McSween, University distinguished professor of Science and department head of the Geological Sciences Department, is a co-investigator for the spacecraft mission, Dawn , which launched in September 2007.

Dawn will spend the next eight years in space traveling to and analyzing two of the largest known asteroids, Vesta and Ceres, which may hold clues to Earth's early history.

"The real interest in Vesta and Ceres is that they are very old leftover planetary building blocks formed by assembling smaller bodies. These are two of the kinds of bodies that the earth was originally formed from," McSween said.

Dawn is powered by the cost-effective ion propulsion system. Ions generated by solar panels spew out the back of the spacecraft accelerating it forward. While the spacecraft will travel very slowly at first, the engine is never turned off so that over time it builds speed and will eventually be the fastest moving object made by man,  McSween said.

Dawn will take four years to reach Vesta and will then spend eight months analyzing different parameters of the asteroid such as mineralogy, chemical makeup and the spectrum of sunlight that reflects from it.

The spacecraft will then take three years to get to Ceres and will spend six months making the same analyses, McSween said.

Both asteroids are located in the asteroid belt between Mars and Jupiter, but they aren't close together or similar in appearance.

McSween said that Vesta looks like a rock that has been melted, whereas Ceres looks like a ball of ice, but there is rock underneath the ice coating.

"You couldn't pick two more different asteroids than Vesta and Ceres. Both kinds were probably needed to make earth; obviously Ceres has the ice for water," McSween said.

Also working on the project at UT are six graduate students, two undergraduates, and two post-doctoral students.

Graduate student Tasha Dunn has worked with McSween for four years.

"It's hard to say enough good things about Hap. Not only is he one of the top scientists in his field, he's also a dedicated and enthusiastic teacher," Dunn said. "Hap is extremely knowledgeable in all aspects of planetary science and geology in general."

McSween has also been involved with Mars Exploration Rover Mission since its beginning in 2003. The mission was expected to last three months but, "It's like the Energizer bunny. It just keeps going and going," McSween said.

The rovers were sent to Mars to look for signs of water and life. McSween estimated that the information provided by the rovers will take over 20 years to analyze.

Both rovers are showing their age. The solar panels that power the rovers have become covered with dust over the years and the rovers are beginning to slow down. The upcoming winter on Mars is the next big obstacle for them.

During the winter on Mars, the sun stays lower on the horizon so the rovers must be placed at an angle that will allow the solar panels to receive more direct sunlight and keep the rovers alive.

McSween and other scientists working on the mission are trying to find a safe haven for the rovers where they can spend the winter.

He said that he spends about one week of every month doing daily teleconferences with scientists in the United States, Canada, Germany and France, along with engineers at the Jet Propulsion Laboratory in Pasadena, California, to dictate the two rovers' actions.

McSween has been a faculty member at UT for 30 years and head of Geological Sciences department for 10 years.

His interest in geology has been life-long, but planetary science became especially interesting around the time of the Apollo missions to the moon. The transition of geology on Earth to include the geology of astronomical bodies has been an exciting period of his career, McSween said.

"They're not points of light anymore. They're not objects you study through the telescope. They're objects where we get information about the rocks and the soil which requires geologists," McSween said.

In his time at UT, the geology department has also broadened its fields of study and was renamed the Earth and Planetary Sciences Department.

McSween received his undergraduate degree in Chemistry from the Citadel, his master's degree in Geology from the University of Georgia, and his Ph.D. in Geology from Harvard University, and is the namesake for asteroid McSween 5223.