Guest Author - Barbara Melville

It is very unlikely that the asteroid Apophis will impact Earth in the foreseeable future. It will pass close to us on April 13th 2029, and again in 2036. There is a small chance that on the first of the two visits, the effect of the Earth’s gravity will dangerously alter Apophis’s trajectory, resulting in impact in 2036. The odds of such an impact are currently estimated at 1 in 45, 000.

Apophis is around 210-330 meters (690-1080 feet) in diameter and will get no closer than 29,470 km (18,300 miles) when it passes in 2029, according to NASA’s Near Earth Object Program website (Predicting Apophis’ Earth encounter in 2029 and 2036). When it flies by in 2029, it will be probably be visible to the naked eye.

Can we do anything to protect ourselves from dangerous NEOs? Yes, by learning. One possibility is finding a way to deflect such objects, thereby changing their trajectory, an idea space agencies are seriously considering. This is a very real example of how the work of astronomers can directly benefit people around the world.

Apophis was provisionally named “2004 MN4” (2004 was the year of discovery), and initial observations indicated that the risk was much higher. If you’re interested in reading up on Apophis (or you have to for school) remember to look at the publication dates of any articles you come across, in case they contain this older information.

Also, keep an eye out for sensationalism – an “end of the world” story makes for a snappy headline. For example, there was a popular news story about a 13-year-old boy who had corrected NASA with new (and frightening) information about Apophis, the main claim being that the chance of impact was much higher than NASA had predicted. NASA released a statement saying that this story was fabricated.

For information on the numbers, read Predicting Apophis' Earth Encounters in 2029 and 2036 on the NASA Near Earth Object Program website. For the truth behind asteroid threats, Phil Plait’s book Death from the Skies (published by Viking in 2008) contains an excellent chapter on potential impactors, entitled “Target Earth: Asteroid and Comet Impacts”.

Sources

Predicting Apophis' Earth Encounters in 2029 and 2036, NASA Near Earth Object Program website, accessed: 14th December 2008.

99942 Apophis (2004 MN4) Earth Impact Risk Summary, NASA Near Earth Object Program website, accessed: 14th December 2008.

NASA Statement on Student Asteroid Calculations, NASA Jet Propulsion Laboratory site (Mission News), accessed 14th December 2008.

Mission Analysis and Design: May we deflect asteroids?, ESA Mission Analysis website, accessed: 14th December 2008.