 |
|
 |
 advertisement
| |
|
|
|
|
|
Kevlar vs. Comets: Bullet-Proof Craft to Get Closest Comet Views Ever
By Heather Sparks
Staff writer
posted: 07:00 am ET
26 December 2001
|
contour_mission_011211.4The bright glowing heads and long streaking tails of comets have always excited curiosity among scientists and backyard stargazers, but a dangerous aspect of these features stalls deep scientific understanding of the icy time capsules from our solar system's earliest days. A comet's tail can be 100,000 miles long. The head, or coma as it is called, creates a dense shroud for hundreds of miles around the heart of a comet. Ground-based observations cannot penetrate these features to see the frozen, rocky nucleus, because the enveloping gas and dust reflect too much sunlight. And these tiny grains of dust can inflict a lot of damage to a modern machine in space. Impact speeds of comet dust on a spacecraft can top of 63,360 mph (102,009 kph). "The equivalent is bullets," says Ed Reynolds, an engineer and Johns Hopkins Applied Physics Lab. Only a handful of spacecraft have ever made it close enough to see the surface of a comet. The most recent, the unprotected and unprepared Deep Space 1, dodged the bullets of comet Borrelly in a daring flyby on Sept. 22 to produce the best comet images made to date.able -->  | | SCIENCE TUESDAY | | | | | |  |  | Images |
| | | 
 | This fabric is woven from Kevlar, a synthetic fiber made of carbon. It is five times stronger than steel. Seven sheets of it, and 10 sheets of another synthetic material called Nextel will make up the spacecraft's dust shield. The shield will be all that protects CONTOUR from at least two comets' bullet-like dust. Click to enlarge.
| |
| | | 
| This is an artist's representation of the CONTOUR spacecraft approaching a comet. The layered dust shield is facing the comet, while the instruments peek out from the sides, surrounded by solar panels. CONTOUR will hibernate for most of its 6 year mission, only to turn on for meetings with the comets, and for its Earth swing-bys. Click to enlarge.
|
| |
| | | 
| The Italian spacecraft Giotto took the first picture of a nucleus of a comet on March 13, 1986. Halley's comet was found to be very porous, with most of its ice melted away. The Giotto spacecraft came within 500 miles of Halley, while CONTOUR will be getting almost 9 times closer to Encke and SW3. Click to enlarge.
|
| |
| | | 
| This is the Oort Cloud, the outer limits of our solar system. Comets reside within it millions of miles apart, up to 50,000 times further away from the Sun than Earth. With a gravitational tug from the outer planets, comets can come toward the Sun, lighting up from its heat, and becoming visible on Earth. Click to enlarge.
|
| |
| | |  | Related SPACE.com STORIES |
| | | | | | | | | | | | | |
|  | TODAY'S DISCUSSION | | | | | | | Cops and comets Soon NASA will use Kevlar, the high-tech composite material from which bulletproof vests are made, to try and get an even closer look at a comet. The CONTOUR (Comet Nucleus Tour) spacecraft is being armored with Kevlar and another tough material, Nextel. The probe will launch in July 2002 and is designed to zoom within a hundred miles or so of the core of two and possibly three comets. CONTOUR should deliver the most accurate measurements ever taken of comets. It is expected to reveal more about the still-mysterious insides of the icy objects than any other instrument, said Reynolds, an engineer on the mission. In November 2003, CONTOUR will sneak to within 62 miles (100 km) of comet Encke and take pictures as sharp as 13 feet (4 meter) per pixel. This is 10 times sharper than images produced by Deep Space 1, which passed within about 1,400 miles (2,200 km) of comet Borrelly. Getting close to a comet is a dangerous game, requiring tremendous precision. Mission planners say that if for some reason the spacecraft gets closer than 62 miles to its target, it may burn up in the roiling clouds surrounding comets Encke, or later, near comet Schwassmann-Wachmann 3. Bad signs, good messengers In the past, comets were thought to be signs from gods of bad things to come. Today astronomers think of comets as time capsules from the beginning of our solar system. Millions of them orbit the Sun, pristine messengers from the past. When the disk of our solar system was just coalescing 4.5 billion years ago, the first comet-sized rocks formed. Many of these rocks collided and made the cores of the gas giant planets. But unlike planets, which are big enough to experience the massive ripping, crashing, melting and molding of geological forces, comets have remained relatively unchanged after all this time. So a comet's nucleus can show scientists what the solar system was like in the very beginning and how it evolved. "In this way, comets give us clues of the early solar nebula in molecular content and from a chemical point of view," said Hal Weaver, a Johns Hopkins University comet expert who is not directly involved with the CONTOUR mission. As the planets were formed, comets still swarmed the solar system, and they rammed into planets more often than they do now. Earth folded these ancient impact craters into itself over the years, but our scarred Moon retains a record of just how frequent impacts were in the first 1 or 2 billion years after the solar system's birth. In fact, astronomers think a flurry of comets might have delivered much of the water that created Earth's oceans, and possibly carbon-based molecules that made life possible. These two possibilities are the driving force behind the CONTOUR mission. Next Page: Sleeping on the trip
1 2 3 | >> Continue with this story >
|
|
|
|
|
|
 |
|
|
