Extreme makeovers in space
Astronomers have worried about the impact that asteroids could have on Earth ever since a theory was proposed in the 1980s that a giant asteroid likely caused the extinction of the dinosaurs 65 million years ago. New research by MIT Professor of Planetary Science Richard Binzel examines the opposite scenario: that Earth has considerable influence on asteroids — and from a distance much larger than previously thought.By analyzing telescopic measurements of near-Earth asteroids (NEAs), or asteroids that come within 30 million miles of Earth, Binzel has determined that if an NEA travels within a certain range of Earth, roughly one-quarter of the distance between Earth and the moon, it can experience a “seismic shake” strong enough to bring fresh material called “regolith” to its surface. These rarely seen “fresh asteroids” have long interested astronomers because their spectral fingerprints, or how they reflect different wavelengths of light, match 80 percent of...