1 A new arrival to the inner solar system is the comet Wild 2. Although the comet has proven to be very different, in fact wild, it did not get its name because it is wild. It was named after Paul Wild, the scientist who discovered it on January 6, 1978, during its first passage near Earth.
2 This comet formed in an area beyond Neptune, 4.5 billion years ago, just after the sun came into existence. Until September 10, 1974, it orbited the sun between Jupiter and Uranus. On that date, Wild 2 passed within 557,000 miles of Jupiter, the largest planet, which brought it into the inner solar system for the first time. This new orbit carried it closer to the sun than ever. It now approaches the sun just inside the orbit of Mars.
3 NASA’s Stardust spacecraft, which was launched in 1999, allowed scientists to see and study
Wild 2. The Stardust examined Wild 2 in a close flyby on January 2, 2004, when it flew just 147 miles from the comet. Only two other comets have been seen up close, both appearing fairly smooth and not very heavily cratered. Scientists were quite sure they knew what they would discover about this comet also.
4 Scientists thought Wild 2 would be a dirty, black, fluffy ball. Were they ever surprised? Instead, results from the Stardust flyby show the Wild 2 to have a rigid surface that supports towering cliffs and peaks 328 feet tall.
5 On Wild 2, there are plunging pits and craters 492 feet deep. In addition, scientists have
discovered two different types of craters on the comet. One type has pits that are rimmed with jagged material ejected from the crater. The other type appears to have flat floors and straight sides. Two large craters of this type are shaped like footprints. The largest one, named Left Foot, is two-thirds of a mile in diameter. The entire comet is only three miles across. Photographs taken by the Stardust have allowed scientists to develop a map of Wild 2 that shows only large craters like Left Foot.
6 Scientists were also surprised by more than two dozen jets shooting chemicals from inside the
comet. Three gigantic jets hit the spacecraft with millions of particles. Twelve particles actually
penetrated the top layer of the protective shield of the spacecraft.
7 So, why are scientists so interested in visiting a comet-like Wild 2? Because Wild 2 has made only five trips around the sun, it is quite new to the solar system. It still has most of its dust and gases. Each time a comet passes close to the sun, part of it is burned off. This comet has not had a chance to change very much from its original condition 4.5 billion years ago. It holds great interest for scientists. Wild 2 is in the perfect place for scientists to view it. Authorities were able to find a flight path that allowed the Stardust spacecraft to fly by the comet at only 13,600 miles per hour, which is considered a low speed. Because of this low speed, more than 1,000 particles of dust were captured by collectors shaped like catchers’ mitts. At a higher speed, the dust would have blown right through the collectors and out the backside. These samples of dust zoomed back to Earth inside a capsule.
8 The samples are being studied at NASA’s Johnson Space Center in Houston, Texas. All of the
information gathered by the Stardust should help scientists improve our understanding of the formation of the solar system.
Question
1. Why does the author compare Wild 2 with the two other comets that have been seen up close?
Responses
A. to give information about the different types of craters discovered on Wild 2
A. to give information about the different types of craters discovered on Wild 2
B. to show how closely scientists were able to study the comets
B. to show how closely scientists were able to study the comets
C. to emphasize that few comets have been viewed at this range
C. to emphasize that few comets have been viewed at this range
D. to explain what scientists expected to find in Wild 2
D. to explain what scientists expected to find in Wild 2
