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New NASA mission to explore early solar system

By S.M. Callimanis
Arizona Daily Wildcat
Wednesday Jan. 9, 2002

UA astronomer part of Dawn team

Scientists will soon know a lot more about the solar system's history due to a newly approved NASA mission, which will examine the composition of two asteroids.

Mark V. Sykes, a University of Arizona astronomer who is part of the science team, said the Dawn mission - which is scheduled to be launched in 2006 - will reveal a great deal about the early solar system by orbiting Ceres and Vesta, two asteroids in the belt between Mars and Jupiter.

"We're going to learn a lot," Sykes said. "We're going to see these new worlds up close, see a few million years after the beginning of the solar system."

Ceres and Vesta, the largest asteroids known, were also two of the first bodies that formed in the solar system. Because the evolution of these small planets was interrupted by the formation of nearby planets, they remain as relics from the first few million years of the history of the solar system.

Scientists involved in the mission see it as "going back in time to visit planets whose growth has stopped in their early stages," said Dawn principle investigator Christopher Russell, a professor of geophysics at UCLA.

"We can't strip away Earth to get to its beginning, but we can go out into this early part of the solar system and take a look at these little bodies," Russell said. "The basic essence of the mission is that it's a journey not only in space but in time."

Announced last month as one of the two latest proposals selected for NASA's Discovery program, Dawn represents the program's goal of "faster, better, cheaper planetary missions," according to the NASA web site.

Earlier missions were able to orbit only the asteroid Vesta and rendezvous with one or two others, Sykes said. Due to technological improvements, this mission will also be able to go to Ceres, enabling the scientists to compare data from both surfaces, he said.

Dawn, a $300 million effort, is the first mission of its type to use an electric propulsion system in planetary exploration. Electric propulsion uses a gentle acceleration for a long period of time. This allows it to have a smaller fuel mass, which aids in maneuverability and efficiency.

While in orbit around the two asteroids, instruments on the Dawn mission will map their surfaces, take measurements of x-rays and gravity fields and find abundances of certain elements. This will give scientists important information about the shape, size, composition and mass of "the early stages in formation of planets similar to earth," Sykes said.

"These are like planetary embryos," he said. "Ceres is especially interesting because it is like a fossil from that time."

Another goal of the mission is to learn how water mobilizes in planetary bodies by contrasting the data from Vesta and Ceres. Ceres is farther from the sun than Vesta and its primitive surface is wet and icy. Contrasting it with Vesta's evolved dry surface can teach scientists about the transition from dry to wet bodies and the formation of water in the solar nebula, Sykes said.

The Dawn mission will launch in May 2006. It will arrive at Vesta in 2010 and orbit for a year, then will arrive at Ceres beginning in August 2014 and will stay there for another year.

Until the launch, scientists on the Dawn team will concentrate on reviewing the design, building the instruments, and going through "every nut and bolt to make sure nothing was overlooked," Sykes said.

Information from the mission will be available to the public on the web prior to launch and throughout its nine years in orbit.


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