http://www.wired.com/wiredscience/2010/09/asteroid-double-whammy-near-earth-tomorrowThese two objects were only found on Sunday, and both are pretty small. One already missed and the other is predicted to miss at 5:12 PM EDT today.
The interesting thing to me is that I checked Nasa's risk chart, which has been updated since the Wired article was written, and if I'm reading this correctly the second object (2010 RF12) now tops Nasa's list of potential impacts:
http://neo.jpl.nasa.gov/risk54 close passes at the earth in the next 100 years (that's how far out they bother to calculate them), totaling a greater than 1 in 100 chance to hit the earth, if I understand it correctly. That could be only because its orbit is still not well defined seeing how they just discovered the thing. The problem is that its so small, once its further away they won't be able to see it any more, and every time it passes the earth its orbit gets perturbed, so any error in the calculation gets magnified, which probably means a large statistical chance for it to hit us.
So did we find these two rocks only three days in advance because we're only now looking that hard, and they are too small to see further away? Were we lucky to even see these objects? Can we expect Nasa's list of potential impacts to be dominated by small rocks that will do little damage as we look harder for them? How much damage would a 20-40ft rock really do?
I'm not saying I'm worried, but I do think its interesting.
