UT Geologist To Analyze Asteroid

KNOXVILLE, Tenn. — A University of Tennessee geologist is on a team of planetary geologists who will analyze the images from Deep Space 1 when the NASA craft flies by an asteroid late this month.

Dr. Dan Britt will be at the Pasadena Jet Propulsion Laboratory on July 28 when the Deep Space 1 spacecraft flies within three to five miles of Asteroid 1992 KD, a cigar-shaped chunk of rock about three quarters of a mile wide and a mile and a quarter long. The first photos from the fly-by should be available on July 30.

If the flight goes as planned, Britt will analyze images of the asteroid to determine its structure and composition. He said that technological advances on Deep Space 1 will allow the craft to maneuver closer to the asteroid than has been possible on any previous flight.

The spacecraft will fly within six to eight kilometers (three to five miles) of the asteroid’s surface, about 100 times closer than the nearest previous flight, Britt said. “That will allow us to see surface features as small as two meters (6.5 feet).”

Deep Space 1 can fly so close because it uses a new guidance system called autonomous navigation, which continuously adjusts the craft’s path without instructions from mission control. Earth-guided craft can make only limited path corrections because at deep-space distances radio commands traveling at the speed of light require several minutes to make a round trip.

The craft also makes pioneering use of an ion propulsion system, the first use of that technology to power a deep-space mission. In 2001, it will fly past another asteroid and a comet.

Britt said there’s no danger of a collision between Earth and 1992 KD. The path of the asteroid comes inside the orbit of Mars but does not cross the orbit of Earth. The fly-by will give astronomers a fuller understanding of the geologic structure and make-up of asteroids and comets that could collide with Earth.

“There are 19 types of asteroids that can be recognized from their colors,” he said. “We know what half are like, but the make-up of the rest is just a collection of vague guesses.

“The actual structures could vary from that of a soggy dirt clod to a chunk of steel.”

Britt said that Earth’s geologic record shows evidence of asteroid collisions that have caused extinctions of various species, including the dinosaurs. There are an estimated 1,500 asteroids larger than 1 kilometer in diameter with orbits that cross Earth’s; so far only about 300 of these have been discovered and tracked.

“We’ll be lucky if we discover half of them in the next 10 years.”

Kilometer-sized asteroids can produce explosions that will affect whole continents, and there is ample evidence of impacts from the more numerous smaller asteroids, Britt said. A 20-megaton explosion caused by an asteroid with an estimated diameter of 50 meters (55 feet) created Arizona’s mile-wide meteorite crater about 50,000 years ago.

“This size of impact happens about every 50,000 years in the geologic record,” he said.

Britt, who received his Ph.D. at Brown University, came to UT in early July from the University of Arizona in Tucson. He was project manager of the camera and deputy leader of the imaging team for the Mars Pathfinder project in 1997.