While the shuttle is in space and our attention is tilted upward, it's worth thinking about what else is up there, especially an asteroid named 99942 Apophis. When this object - a little more than a thousand feet across - was first discovered last year, astronomers estimated that it had a distant chance of striking Earth in 2029. After closer observation, it seems likely that this asteroid will still pass very near our planet, but without striking it. There is still a possibility, however, that as it swings by it may hit a gravitational "keyhole," shifting its orbit far enough...