Earth faces higher risk of devastating asteroid strikes, study finds.

A NASA-funded study presented at the Lunar and Planetary Science Conference suggests that big asteroids hit Earth more often than previously thought, based on satellite data. The study used high-resolution data from several Earth-observing satellites to examine three impact craters. Garvin's team suggests that large rings are visible in the data, showing that the craters are tens of miles wider than previously measured. That size adjustment, in turn, implies that the impacts were far more powerful than previously cataloged. However, some scientists are urging more critical examination of the results before fully revising all of our estimates for space rock encounters.