by Zoë Pollock
We may be able to prevent it:
We humans need not wait, like dinosaurs, for the next big rock to drop. We have an advanced understanding of the heavens and a spacefaring technology that could soon enable us to alter the orbits of any celestial object on a collision path with us. That capability just might come in handy. We got a taste of the challenge in December 2004, when scientists at NASA and the Jet Propulsion Laboratory (JPL), in Pasadena, Calif., estimated there was a nearly 3 percent chance that a 30-billion-kilogram rock called 99942 Apophis would slam into Earth in 2029, releasing the energy equivalent of 500 million tons of TNT.
That’s enough to level small countries or raise tsunamis [PDF] that could wash away coastal cities on several continents. More recent calculations have lowered the odds of a 2029 impact to about 1 in 250 000. This time around, Apophis will probably miss us—but only by 30 000 km, less than one-tenth of the distance to the moon. But let’s not rejoice too quickly. We know next to nothing about that asteroid’s porosity, composition, and tensile strength. It’s possible that tidal stresses during its 2029 approach could cause it to break apart, adding to the odds of an Earth impact during another rendezvous further down the line.
The Dish 