Red Dawn

Once again, Terra narrowly missed being hit by an asteroid. On March 2nd 2009, a large space rock sped past the earth traveling between 3,000 and 30,000 mph. Not a lot of people really knew much about it. In fact, it was only discovered 2 days before the flyby. I found out about it when my brother called to tell me that he had noticed a bright object in the sky and had called NASA about it. NASA told him that it was a space rock and that it would likely not collide with the planet. That's refreshing!

2009 DD45, the designation for the space rock in question was approximately 30m in diameter. JPL discovered this by taking the different size ranges from photos and taking an average. DD45 was likely spinning so fast that it was difficult to calculate. In any event, the 30m (that's 90 feet for those in Oak Cliff) space rock was about the same size as the surmised "meteor" that exploded over Podkamennaya Tunguska River in 1908. I put meteor in quotations because according to physicists the object exploded before impact rather than hitting the ground and then exploding. Kind of ironic that it almost happened again 100 years later.

By most estimates the Tunguska Event, as it is now known, leveled about 80 million trees in Siberia and exploded with the power of 1,000 Little Boy atomic bombs. For comparison it only takes 1 Little Boy to destroy an average-sized city (see Hiroshima blast for more information). With that much power it could easily have destroyed an entire metropolitan area.

Today, there is little forewarning once these objects are discovered. I realize that JPL thought it was highly unlikely that the DD45 asteroid would actually collide with the Earth but that gives me little comfort (see Mars Climate Orbiter mission for information on the accuracy of JPL's trajectory calculations).


References

NEO 2009 DD45
http://planetary.org/news/2009/0302_Space_Rock_Swoops_by_Earth.html

Mars Climate Orbiter
http://www.jamesoberg.com/mars/loss.html