Update on asteroid hitting Mars: Now 1-in-28

William Atkins
Friday, 04 January 2008 19:16

Science - Space

The chance that asteroid 2007 WD5 will hit the planet Mars on January 30, 2008, has been slightly reduced from 1-in-25 (4%)  to 1-in-28 (about 3.6%) based on observations at the Magdalena Ridge Observatory.            

Astronomers at the astronomical observatory Magdalena Ridge Observatory (MRO) in Socorro County, New Mexico, made the observations that slightly changed the chance of the asteroid-red planet collision.

The observatory, which is located about 30 miles (48 kilometers) west of the city of Socorro, is operated primarily by New Mexico Institute of Mining and Technology and the University of Cambridge (England). It stands at an elevation of about 10,600 feet (3,180 meters).

Asteroid 2007 WD5 is a near-Earth object (NEO), which means that it could at some point in the future also have a chance of impacting our planet Earth.

NEOs include such bodies as comets, asteroids, and large meteoroids whose orbits bring them close to the orbit of Earth. Usually they are considered NEOs if their closest distance (perihelion, distance from Sun) is less than 1.3 astronomical unit (AU). One AU is the average distance between the Sun and Earth, about 93 million miles (150 million kilometers).

NASA has been charged by the U.S. Congress with cataloguing all NEOs that are at least 0.6 miles (1 kilometer) in width. About 800 NEOs have so far been listed, but most estimates by astronomers place another 200 such objects as being still uncharted.

Many countries have joined Spaceguard in order to make a concerted effort to identify all possible threats from NEOs to Earth.

In 2008, Mars is the target for the asteroid. If it does hit the Red Planet, 2007 WD5 will be traveling at about 30,000 miles (48,000 kilometers) per hour. At such speeds, it will create an impact crater of over one-half mile (800 meters) wide if a direct hit is made.

Such an impact is being compared by astronomers with the 1908 Earth-explosion in Siberia. Called the Tunguska Event (or Tunguska Explosion), the gigantic explosion near the Podkamennaya Tunguska River occurred on July 13, 1908 (Gregorian calendar), or June 30, 1908 (Julian calendar).

A large meteoroid or comet—anywhere from 100 to 4,000 feet (30 to 1,200 meters) in diameter—exploded in the Earth’s atmosphere—about three to six miles (five to ten kilometers) above the Earth’s surface—and resulted in nearly complete devastation over 830 square miles (2,100 square kilometers).

Although hitting in a mostly unpopulated area, such an explosion near a large city has the potential for causing massive death and injuries to people and destruction of property. Such a possibility is the reason why the study and identification of near-Earth objects is important to all of humankind.

Because of large uncertainties in predicting these NEOs, astronomers can only give vague estimates on the chance of one hitting Earth. Right now, the general consensus is that the chance of a NEO hitting Earth in the next few decades is “small but real.”