Last Friday, February 15, 2013, a 150-foot asteroid safely passed Earth. This was the closest known flyby for a celestial body of its size, missing Earth by only 17,000 miles.

To put a scale on this, our geostationary satellites are about 22,000 miles from Earth. Thus, DA14 passed inside the geostationary orbit. That's closer than some satellites. Furthermore, this rock is the size of half a football field. Ouch!

Coincidentally, a much smaller meteor did enter the atmosphere and exploded above Russia's Ural Mountains. Check YouTube for video. Astronomers think the two events were strictly a coincidence, because the two objects were traveling in opposite directions.

In recent days asteroid stories have been frequent. Just last fall a graduate student presented a paper at the International Astronautical Congress in Naples, Italy.

He came up with the idea of firing paint balls at an asteroid headed for a collision with Earth. This paper won the 2012 Move an Asteroid Technical Paper Competition sponsored by the United Nations' Space Generation Advisory Council, a competition which solicits creative solutions from young professionals.

The hypothesis here is as follows. Given sufficient warning an asteroid could be diverted by increasing the asteroid's albedo, or reflectivity.

Thus, the paint would have to be light-colored and applied to the asteroid with sufficient advanced notice to allow solar pressure to divert the large body's trajectory enough to bypass Earth. This student suggested that his plan would work in two different ways.

Paintballs themselves could impart a slight momentum change to the asteroid, diverting it only slightly, but not enough to avoid Earth. The main effect would come from the paint's increase in reflectivity on the asteroid.

Thus, the pressure of photons coming from the sun, acting over enough time, could result in a large shift in course.

The paper concludes that the course of asteroid Apophis, a 27-gigaton rock that is expected to pass close to Earth in 2029 and in 2036, could be changed enough to miss Earth. He estimated that 5 tons of paint would be sufficient to cover the 1,480-foot-diameter asteroid.

Calculations indicate it will take roughly 20 years of exposure to the paint in order to deflect the asteroid away from an Earth collision. Now, let me see if I have this right.

The first close approach will be in 2029 and the paint has to be in place for 20 years. A quick calculation indicates that we are a little late already. Oh well, maybe someone will come up with a better idea in time to divert the next large asteroid.