Ever wonder why asteroids appear so shiny and new after perhaps 4 billion years wandering the solar system? Space.com reports on a new study revealing passing asteroids get shaken up by the Earth’s gravitational pull when they pass too closely. And this process rids them of their reddish skins, revealing a smooth, grey finish underneath.

The study was lead by Richard Binzel of MIT. As Binzel explains, when asteroids fly through the universe, they become weather beaten. The asteroid's top coat becomes reddened from the onslaught of charged particles coming off the sun. It is almost like getting a sun burn. According to Binzel, "Any part of the surface that's facing into the sun is hit by the solar wind, which damages the mineral grains and turns them red."

And when the asteroid gets too close, the Earth’s gravity may induce small quakes that shake up the outer skin of the flying object. This causes the weathered pebbles on their surface to turn over, revealing their cleaner undersides. As Binzel told Space.com, "All of the particles that got reddened are going to flip over and you're going to have new material that's fresh now out facing the sun."

The researchers came to these conclusions after studying 95 near-Earth asteroids over a period of time. Using a process called spectroscopy, they identified the colors of the asteroids and then combined this data with measurements of the NEAs' orbital histories.

This information may prove handy when the large asteroid Apophis travels near Earth in 2029. Scientists plan to study the way the asteroid shakes and rattles when it passes by. This in turn could help scientists understand the nature of other potentially dangerous asteroids.

For further reading: Earth causes asteroid quakes.

Earth causes mini-quakes in passing asteroids
Tiny quakes shake up the asteroids, changing the outermost surface. This movement explains why red asteroids appear so grey and polished.