In the wake of my last post, I was astonished to discover that later today an asteroid the size of an aircraft carrier will pass within a mere 323,00 kilometers of Earth. (For those of you without sense of scale for either one of those numbers, that's something about 400 meters in diameter coming closer to Earth than the Moon.)Asteroid 2005 YU55 will do its fly-by at 6:28 EST, and during its run it will be 11,000 kilometers within the Moon's orbit. By the standards of cosmic distance, that's like having a bullet get closer to your face than the tip of your nose - and in this case, the bullet is moving at 46,000 kph.
The good news is that according to the good people at NASA's Jet Propulsion Laboratory, there is no chance that this object will hit the Earth either during this visit or any time in the next 100 years. Nonetheless, the idea of a chunk of rock the size of a city block getting that close makes me more than a little nervous.
However, the adjacency of YU55 to Earth logically suggests that it might just as easily have hit the Moon. (After all, the Moon is a sort of orbital poster child for impact craters - just look at it.) Hmmm...I wonder what the effects of a really big asteroid hit on the Moon would be? Presumably a large enough hit might shatter it, making us the recipient of a lot of collateral damage from fragments. A slow breakup might give us an orbital ring à la Saturn. But I think it's unlikely we'd get something that looked anything at all like the half-completed Death Star from Return of the Jedi, as much as I hate to disappoint you Star Wars fans.
- Sid
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