 |
 |
||
 |
|
||
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
||||||||
 |
Planetary News: Near Earth Objects (2007)Asteroid Misses Earth, Threatens Marsby Amir AlexanderDecember 21, 2007
Astronomers in NASA’s Near Earth Object (NEO) monitoring program are tracking the trajectory of an asteroid estimated to be 50 meter (160 feet) wide that is expected to cross Mars' orbital path early next year. Observations provided by the astronomers and analyzed by NASA's NEO Office at the Jet Propulsion Laboratory in Pasadena, Calif., indicate the object is likely to pass within 50,000 kilometers (30,000 miles) of Mars at 5:55 a.m. EST (10:55 UT) on Jan. 30, 2008. There is also a 1 in 75 probability that the asteroid will slam into the planet at that time. Designated 2007 WD5, the asteroid was discovered on November 20 by NASA-funded observers searching for possible Earth-impactors. At that time of its detection the asteroid had already made its closest pass of the Earth, closing to within 7.5 million kilometers (4.7 million miles) on November 1, and was moving towards Mars. The original detection was made using the 1.5 meter telescope on Mount Lemmon, near Tucson, Arizona, and was followed up with observations at Kitt Peak, Arizona, and the Magdalena Ridge Observatory in New Mexico. Taken together, the observations indicated that although Earth was safe from 2007 WD5, our smaller neighbor Mars may not be. "Right now asteroid 2007 WD5 is about half-way between the Earth and Mars and closing the distance at a speed of about 27,900 miles per hour," said Don Yeomans, manager of the Near Earth Object Office at JPL. "Over the next five weeks, we hope to gather more information from observatories so we can further refine the asteroid's trajectory." If the asteroid does indeed strike Mars, it will impact somewhere in an 800 kilometer (500 mile) wide band that crosses the Martian equator. The southernmost boundary of this band lies slightly to the north of the region explored by the rover Opportunity. Though close, however, the rover is clearly outside the zone of possible impact.
"We estimate such impacts occur on Mars every thousand years or so," said Steve Chesley, a scientist at JPL. "If 2007 WD5 were to thump Mars on Jan. 30, we calculate it would hit at about 50,000 kilometers per hour (30,000 miles per hour) and might create a crater more than half-a-mile wide." Such a collision could release about three megatons of energy. Scientists believe an event of comparable magnitude occurred here on Earth in 1908 in Tunguska, Siberia, but no crater was created. The object was disintegrated by Earth's thicker atmosphere before it hit the ground, although the air blast devastated a large area of unpopulated forest. Though the chances of a collision between Mars and 2007 WD5 are slim, planetary scientists are nevertheless hoping that the asteroid will thread the needle and strike the red planet. If this were to happen, it would be the first time that scientists would get a chance to observe the impact of an asteroid on a terrestrial planet such as Mars or Earth. This is especially significant, because current theories suggest that bombardment by space rocks played a key role in our own planet’s evolution, from the introduction of water to the demise of the dinosaurs. And while scientists do possess effective computer models of the dynamics of an asteroid impact, there is no substitute to the actual observation of a natural event. In 1994 comet Shoemaker-Levy 9 struck Jupiter, providing scientists with their only close-up view of a celestial collision. But Jupiter is a gas giant, and the dynamics of impact are very different than they are on a rocky planet such as Mars.
Did you like this article? Send
it to a friend or share it at:
Slashdot - Digg this - Reddit - Del.icio.us - Newsvine - NowPublic |
|||||||
 |
 |
|||||||
[ what is this? ]