Spacecraft “Dawn” reaches the Asteroid Belt

Last July a NASA-sponsored spacecraft called “Dawn” slipped into orbit about the first of its planned destinations — the asteroid Vesta, which is the second-largest asteroid in the Asteroid Belt between Mars and Jupiter. About 5 percent of meteorites recovered after falling to earth are believed to have come from Vesta’s surface.

The Asteroid Belt is the name given to hundreds of thousands of asteroids, both large and small, that orbit the Sun in a band of space that stretches partway between the orbits of Mars and Jupiter.

Were the asteroids once a planet in the past that broke apart?

“Quite the opposite,” said Christopher T. Russell, the principal investigator of the Dawn mission. “The material tried to accumulate into a planet but never was able do so.”

Russell coordinates and directs the science aspects of the Dawn mission as a part of his work as a professor in the Institute of Geophysics and Planetary Physics at UC Los Angeles. The Jet Propulsion Laboratory (JPL) in Pasadena is in charge of the actual operation and flight of the space vehicle.

Elizabeth Palmer is a first-year graduate student who is working as a research assistant under Russell’s guidance at UC Los Angeles. She studied astronomy as an undergraduate at Case Western Reserve University in Cleveland, Ohio, but ended up deciding that planetary science was a better fit for what she wanted to do. She was able to find a planetary science internship at JPL.

While at JPL, Palmer began learning about the technique of interpreting radar signals which have been bounced or grazed off the surface of a planetary body and received on Earth. She hopes to be able to do the same type of work interpreting microwave transmissions from Dawn that have grazed the surface of Vesta in order to determine aspects of Vesta’s make-up, such as whether ice is present on the surface and in what amount.

“It’s an opportunistic experiment that’s not perfect, since it’s hard to alter such concrete mission plans to the way that would be most ideal for our microwave experiment to work best,” Palmer said. “We are just waiting and hoping the geometry will work at some point.”

If Dawn is able to successfully graze signals off Vesta, which are then successfully received here, Palmer will be able to compare that data with experimental data obtained from meteorites found on Earth. This mineral material was likely knocked off Vesta’s surface as a result of ancient collisions in space.

Dawn gets its name from its primary purpose, which is the study of our solar system’s early history. Russell often stresses that he views Dawn as being a kind of time machine traveling back in time, since both Vesta and Dawn’s second target, Ceres, have likely preserved evidence of the Solar System’s formation in the contours of their crust and in their composition. Both Vesta and Ceres were formed 4.6 billion years ago.

Dawn is currently scheduled to leave Vesta in August later this year and enter orbit about Ceres, the largest asteroid, in February 2015. According to Russell, it is the long-term thrust enabled by Dawn’s efficient ion-propulsion system which made the mission cost-effective and a visitation to two asteroids possible as a project goal.

BRIAN RILEY can be reached at science@theaggie.org.

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