Scientists from various research laboratories will spend this weekend in suburban Baltimore studying images captured from an unexpected flyby of the biggest asteroid ever observed up close.
The Near-Earth Asteroid Rendezvous craft flew by asteroid 253 Mathilde at about 8:56 a.m. EDT Friday. A CCD camera mounted on the craft snapped 534 images in the process - the first of which was uploaded to the Web site of Johns Hopkins University's Advanced Physics Laboratory. From the photos, researchers hope to learn more about Mathilde's shape and color in addition to whether satellite bodies are orbiting around it.
"[Mathilde] is sort of a stealth asteroid. It's big - 137 to 140 miles in exacting diameter - very black ... one of the blackest objects in the solar system. And very little is known about it," said Dr. Donald K. Yeomans, leader of the NEAR radio science team based at NASA's Jet Propulsion Laboratory.
Asteroids are space-borne fossils which hold clues as to how the solar system was formed. Space scientists launch craft such as NEAR to gather data that will help determine an asteroid's diameter (about 40 miles), mass, and mineral composition as well as its geology. They also hope to draw a relationship between asteroids - which are heated material - and comets - made of frozen materials - said Dr. Andrew Cheng, NEAR project leader at the Advanced Physics Laboratory.
Originally designed to orbit asteroids, NEAR had to undergo several adjustments to deal with a flyby so pictures could be taken. In orbit - which NEAR will be in January around the asteroid Eros - NEAR will travel 10 miles above the surface of the asteroid at a speed of 10 mph. By contrast, the craft sped by Mathilde at 22,000 mph, coming only as close as 750 miles - roughly the distance between Los Angeles and Denver.
This NEAR mission represents a number of firsts for space exploration. As part of the Discovery program, NEAR is the result of combined efforts by several research laboratories, all supported by NASA. In addition, Mathilde has provided the first images of a C-type asteroid, one that is carbon-rich. NEAR has also set the record for solar-powered crafts conducting science experiments at the farthest distance ever from the sun - a distance that is roughly twice as far as the Earth is from the sun, Yeomans said.
Because of the distance - and the limited time that the solar panel will be exposed to the sun - NEAR operated at one-sixth of its normal power. This cut down on the number of science experiments researchers could conduct. For Mathilde, that means only radio waves - used to track its path - and imaging - the results of which are the photos - will be able to happen.
Fortunately, scientists will have a second opportunity to observe Mathilde around October or November, when the asteroid will come close enough to Earth that radar receivers will be able to pick up its path to confirm the data the researchers are gathering from NEAR's photos.
