In a spirit of calm, we ought to point out that NASA says close calls like these happen, on average, almost daily.
Ned Potter | blogs.abcnews.com
A decade ago, this was the stuff of movies — think “Armageddon” and “Deep Impact” — but one of the more memorable lines from back then was that the planet would be whacked by something “the size of Texas.” Asteroids the size of today’s passersby enter the earth’s atmosphere about once a decade, mostly harmlessly.
Of course, every now and then — remember the theory about the death of the dinosaurs — something hits us that is not harmless. The object believed to have ended the Cretaceous period is estimated to have been about six miles across. And that’s why the astronomers in Arizona didn’t have much of a Labor Day weekend.
Update: Wayne Farley asks a good question: How quickly are either of these objects moving? The answer, according to the Near Earth Object program at NASA, is a maximum of about 6 km/second –about 13,400 mph — for 2010 RF12 and 10 km/second — 22,370 mph — for 2010 RX30, relative to us. (For comparison, a spacecraft in low earth orbit moves at about 17,000 mph relative to the earth’s surface.) If you want to have some fun, the Jet Propulsion Lab has an interactive graphic of the orbit of 2010 RF12 and other objects HERE.