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Scientists release dramatic photos of asteroid
June 30, 1997
Web posted at: 7:18 p.m. EDT (2318 GMT)In this story:
WASHINGTON (AP) -- Scientists call it a stealth asteroid, meaning it is huge and dark, reflecting just four percent of the sunlight that strikes it.
It's name is "Mathilde," and scientists at the Johns Hopkins Applied Physics Laboratory Monday released dramatic new photos that show the asteroid is 33 miles across at its widest point.
NASA animation of Mathilde
340K/12 sec. QuickTime movie
More pictures of Mathilde The pictures were taken by the Near Earth Asteroid Rendezvous (NEAR) spacecraft on Friday during a 25-minute flyby. NEAR was launched last year to orbit and study another asteroid, Eros.
At the time of the flyby, the asteroid was about 180 million miles from Earth. The spacecraft sped past it at 22,000 miles an hour, with on-board cameras snapping all the while. At 750 miles, it was the closest approach to an asteroid ever made by a spacecraft.
"We nailed it," NEAR Mission Director Robert Farquar said. "The performance of the spacecraft ... and the NEAR team was, in a word, perfect."
Findings are still sketchy, but preliminary data suggest the asteroid is smaller and less dense than previously thought, under 35 miles across. Scientists estimate that mean density is near the weight of ice, about half the density expected. It has five huge craters, including one that is about 20 miles across and more than three miles deep.
Twice as dark as charcoal
In the photos, Mathilde appears like a gray ball of clay with huge chunks gouged out and pock marks covering every visible surface. "It's all crater. There's hardly any asteroid," Joseph Veverka of Cornell, one the NEAR scientists, said. "This is the most craters we've ever seen" relative to the size of the body."
It hangs in a velvet field of black with the sun lighting one side and sending deep shadows across the craters. The colorless asteroid is twice as dark as ordinary charcoal.
Veverka said the number of craters suggests that Mathilde is "a few billion years old" because it would have taken that long for so many collisions to have occurred.
As old as the planets
That means Mathilde could be as old as the sun and planets, a time capsule made of the basic building blocks of the solar system.
Though the Mathilde flyby is the closest ever to an asteroid, it is not the first. The Galileo spacecraft took pictures of the asteroid Gaspara, in 1991, and of Ida, in 1993.
Astronomers were surprised to find Ida has a small moon, Dactyl. So far scientists have not found any moons around Mathilde, but they are still looking.
NEAR is scheduled to arrive at the asteroid Eros January 10, 1999. It will orbit and map that asteroid for a year and end its mission by landing on the asteroid itself.
Special section:
CNN Interactive's extended coverageRelated stories:
- Scientists thrilled by photos of 'stealth asteroid' - June 27, 1997
- Asteroid will pass near Earth Friday evening - November 29, 1997
Related sites:
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- National Aeronautics and Space Administration
- NEAR Homepage
- Asteroid shapes and spin states from radar and optical data
- European Asteroid Research Node
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