Asteroid 2007 WD5 on a Collision Path with Mars

On November 20th, 2007, astronomers with the NASA-funded Catalina Sky Survey....

On November 20th, 2007, astronomers with the NASA-funded Catalina Sky Survey discovered a new near-Earth asteroid. This object, designated Asteroid 2007 WD5, is worthy of concern. Based upon its magnitude it was estimated to be about 50 meters (164 feet) across. It is traveling at about 28,000 miles per hour. At the time of its discovery, it had already passed within 7.5 million kilometers (5 million miles) of earth. That close approach occurred on November 1, 2007. It streaked past Earth undetected. The 50 meter diameter and tremendous speed of this asteroid would produce major damage if it were to hit Earth on a future orbit. An asteroid this big would hit with a force exceeding any atomic blast that people have produced. Such an impact would blast a hole about the size of Arizona's famous Meteor Crater - nearly one mile across. Astronomers immediately placed Asteroid 2007 WD5 on their "watch list" and began calculating its orbit around the sun. They wanted to find out if future orbits would bring it dangerously close to Earth. NASA has a team of astronomers who detect and track asteroids and comets passing close to Earth. This Near Earth Object Observation Program, commonly called "Spaceguard," calculates the orbits of all known near-Earth objects to determine if they are on a future collision path with our planet. Astronomers with the Spacewatch program at Kitt Peak, Arizona and the Magdalena Ridge Observatory in New Mexico began tracking the asteroid. This tracking gave them important information about its path through space. They used this data to determine that the asteroid was not an immediate threat to Earth; however, it could potentially impact Mars. With minimal data they estimated that it would pass by Mars on January 30th with about one chance in seventy-five of hitting the planet. As the asteroid zipped off towards Mars, astronomers on Earth were carefully searching their space image archives. They were looking for pre-discovery images of Asteroid 207 WD5. They were in luck. Andy Puckett, a recent Ph.D. from the University of Chicago (now at the University of Alaska at Anchorage), found an image taken on November 8, 2007 - about two weeks prior to its discovery - that showed Asteroid 2007 WD5 as a faint dot of light. This image allowed astronomers to accurately determine the position of the asteroid in space at a specific instant in time. This new data enabled them to refine the path of the asteroid's orbit. This new data allowed astronomers to determine that Asteroid 2007 WD5 has about one chance in 25 of hitting Mars! The asteroid will approach the day side of Mars. This will make it difficult to observe. The best prediction is that it will miss Mars by a mere 50,000 kilometers (30,000 miles). However, this prediction is highly uncertain. The orbit of the asteroid is not known with a great degree of accuracy. Astronomers know that the asteroid will approach Mars through a very long and very narrow window. This window is about a 400,000 kilometers (250,000 miles) long but only about 600 kilometers (350 miles) wide. This window is illustrated in the artist's image at right. Steve Chesley, a scientist at NASA's Jet Propulsion Laboratory estimates that an object the size of Asteroid 2007 WD5 hits Mars about once every 1000 years. He believes that if the asteroid hits Mars the collision will produce an explosion equivalent to about three megatons of energy and produce a significant crater. For now, NASA astronomers and their partners are carefully tracking 2007 WD5, collecting data that will enable them to give a more accurate determination of how close it will approach Mars on January 30th. Stay tuned for updates! The closer the asteroid gets to Mars the more accurately its path can be predicted