Completely unrelated to the event over Russia this morning, asteroid 2012 DA14 will do an extremely close flyby of Earth around 2:25pm EST. 2012 DA14 was discovered a year ago and orbits the sun at almost the same distance we do, only its orbit is inclined by ~11 degrees with respect to ours. This afternoon, it will be traveling from below our orbital plane to above it as it passes within 17,000 miles of us. As the video says, that's closer than our geosynchronous satellites, which is pretty darn close. However, and I can't stress this enough, IT WILL NOT HIT US.
We know this because NASA's Near Earth Object Observation (NEOO) Program has been tracking it since its discovery and has determined its orbit with enough certainty to rule out any chance of impact. In fact, 2012 DA14's close approach today will actually alter its orbit by moving it inside, or closer to the Sun, than ours.
Unfortunately, 2012 DA14 will make its closest approach over the Indian Ocean, so it won't be visible from the U.S., but it will be live-streamed by several observatories around the world. NASA also has an informative collection of graphics and videos on the flyby here.
The take away from today's encounter with not one but two space rocks is that near earth objects pose a real threat to us. Asteroids the size of 2012 DA14 are predicted to hit Earth once every 1,200 years, but statistically they pass this close to Earth every half-century or so. In general, asteroids on scales smaller than this are notoriously difficult to detect as they are dark, rocky bodies that don't emit any light and only reflect a fraction of the light that hits them. It's like if someone threw a handful of sand in a darkened room and you tried to find every piece with only a small flashlight. Luckily NASA has a network of "flashlights" on the look-out, but today should serve as a reminder that there are some objects that will still escape our detection. While we still don't know the exact size of this morning's Russian meteor, Alan Boyle has a great list of past meteor impacts for comparison to 2012 DA14. If you're feeling macabre, Purdue University has a site where you can calculate the impact of a given meteor. And as always, Phil Plait has the answers to all your burning questions.
At this point, it's a numbers game for when we find the next big one headed our way. May the odds be ever in our favor.