Thanks gleeaikin. This tiny little thing ("about 10 meters") could make it through the atmosphere, if it were to be right on time to do it, and if it's a solid piece of rock. But it would be a tinier little thing by the time it hit the ground.
Asteroid 2011 MD [was discovered] on June 22. It has an orbit similar to Earth's.
There's a bunch of these, and PANSTARRS is looking for them. NASA's program has been to locate and identify the big stuff (km and up) but stuff much smaller than a km can do a lot of damage. The Tunguska object was perhaps as much as 100 meters across (estimates range as high as at least 1200 m, as low as 50 m, and this is mostly due to different density estimates), and exploded in an airburst several hundred feet before it hit the ground, knocking down trees for miles.
