Asteroid Near Miss
Written by Jerry Coffey
Radar image of asteroid Apophis.
That close encounter was in December, 2004. It was actually predicted to have a 2.7% chance of hitting the Earth in the year 2029. The chances are still there that it may impact the Earth on its next pass in 2036. An asteroid that is 350 m in length could do quite a bit a damage should it hit the Earth. Apophis broke the record for the highest level on the Torino Scale, being, for only a short time, a level 4, before it was lowered. It stayed a a level 1 for nearly two years.
An asteroid near miss is measured by the Torino scale. The Torino Scale is a method for categorizing the impact hazard associated with near Earth objects (NEOs) such as asteroids and comets It is intended as a tool for astronomers and the public to assess the seriousness of collision predictions, by combining probability statistics and known kinetic damage potentials into a single threat value. The scale scores from 0 to 10 with 10 being a definite impact that will devastate most of Earth. Apophis was the first, and still the only asteroid to score a 4 on the Torino scale.
Shortly before the excitement of Apophis, there were two other asteroid near miss incidents. On June 17, 2002 the LINEAR Spaceguard system discovered Near Earth Asteroid (NEA) 2002 MN, which had passed the Earth on June 15 at a distance of only 120,000 km, one of the closest asteroid fly-bys on record at the time. Based on its brightness, 2002 MN has a nominal diameter of about 100 m, large enough to penetrate through the atmosphere to the surface if it struck the Earth. In March, another asteroid, 2002 EM7, passed within 463,000 km. This asteroid also was not found until after its flyby of Earth. It just goes to show you how much work that is still needed in the study of NEAs.
Asteroid near misses have happened throughout the history of the Earth. Many have collided with the Sun or other planets, even each other. Our advancing technology and knowledge is allowing us to observe these very scary solar objects and get a better feel for what is going on around us each and every day. When Apophis passes again in 2029 and 2036, hopefully, we will be even better equipped to study it and other NEAs.
There is a more in depth description of the Torino Scale at this link. We have several very interesting articles about asteroid near misses and NEAs here on Universe Today. Astronomy Cast offers a good episode on asteroids as neighbors.
Filed under: Astronomy
Tags: asteroid 2004 MN4, asteroid Apophis, asteroid near miss
