Asteroid Might Hit Mars
The Space Rock 2007 WD5 May Collide with the Red Planet in January
An asteroid approximately 60 meters in diameter has a 1-in-25 chance of smashing into Mars on January 30, 2008.
In late November 2007 the Catalina Sky Survey discovered an asteroid heading toward Mars. This asteroid, dubbed 2007 WD5, has an unusually high likelihood of impacting a planet. Space rock and planetary collisions are rare, with only one being witnessed on another planet over the course of human history, when Comet Shoemaker-Levy 9 sank into Jupiter's thick atmosphere to much fanfare in 1994.
Asteroid 2007 WD5 was initially tracked because it comes close to Earth, and investigators wanted to know if Earth was under threat from the asteroid. They discovered it was not but were amazed to see how close it will get to Mars.
Don Yeomans, the manager of the Near Earth Object Office at the Jet Propulsion Lab, says, "Right now asteroid 2007 WD5 is about half-way between Earth and Mars and closing the distance at a speed of about 27,900 miles per hour." If the asteroid that size struck Mars at that speed, it would create a crater similar in size to Arizona's meteor crater.
The most recent large collision with Earth happened in 1908 when an asteroid entered the atmosphere over Tunguska in Siberia, exploding above the ground and flattening an immense swath of land including 60 million trees. Fortunately this region of the world is very sparsely populated and although there were a handful of witnesses, no one was killed.
A Surprise for Scientists
The possibility of an asteroid impacting Mars has surprised a lot of astronomers. The 1994 Jupiter collision was not completely unexpected because Jupiter is the second largest object in the solar system and therefore its gravity would pull in more objects than the other planets. In fact, it is believed that Jupiter may have a protective effect on the other planets by luring asteroids away from them.
Mars is about half as large as Earth and therefore not a large target. It is the second smallest planet in the solar system after Mercury. But its location near the asteroid belt makes it more vulnerable. Mars's two moons, Phobos and Deimos, are actually captured asteroids that have been pulled in toward Mars and assumed an orbit around the Red Planet.
The "Big One" Happening on Mars
If the asteroid does indeed hit Mars, all eyes and telescopes will be turned toward the big event. The impact itself is estimated to occur anywhere along a wide swath of Mars, including just north of where the rover Opportunity is examining the Martian surface.
If 2007 WD5 tears a hole in the surface of Mars, backyard observers with large telescopes may watch for a cloud of dust and debris that could be kicked up into Mars's atmosphere.
Stay tuned for more observations from NASA as they refine the orbit of 2007 WD5 as it approaches Mars over the coming month.
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