Astronomers claim to have found evidence that asteroids that venture too close to Earth suffer cataclysmic landslides, which often shake up their structure, a finding which explains why they look so fresh-faced.
According to the 'New Scientist', the idea explains an old puzzle. Most asteroids are stained dark red by relentless bombardment of space particles. But some asteroids that stray into the inner solar system are paler.
One theory was that they have suffered collisions, exposing fresh rock on their surfaces. Now, a team, led by Richard Binzel of Massachusetts Institute of Technology has confirmed a rival theory.
They calculated the orbital behaviour of 95 asteroids that travel into the inner solar system. Over the past half a million years, some orbits remained aloof from Earth's, and others drifted perilously close to it.
Of the 20 pale asteroids in the sample, every single one had the possibility of a close encounter with Earth. "We've nailed it," Binzel was quoted as saying.
The result implies that Earth's gravity stretches and disturbs asteroids that come too close, perhaps causing landslides that expose underlying rock.