Science: In 2029, a football-field-sized asteroid known as Apophis is going to pass within 35 000 km of Earth. Our planet is not in any danger, but simulations run by Derek Richardson of the University of Maryland, College Park, and his colleagues suggest that Apophis could experience avalanches, albeit very small ones. Pictures of another asteroid believed to be similar to Apophis indicate that instead being solid rock, the two asteroids are clumps of debris loosely held together by gravity. In Richardson's simulation, the tidal force of Earth's gravity caused small, slow-moving avalanches of the lighter pieces of debris on the asteroid's surface. Although astronomers will not be able to see the avalanches directly, IR pictures of the surface could reveal areas that have been uncovered as the surface shifts.
