Mars, not Earth, shakes up some near-Earth asteroids

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The gravity of the Red Planet causes the asteroid's†surface material to shift, exposing fresh material, which†explains the colour variation previously observed.†Reuters The gravity of the Red Planet causes the asteroid's†surface material to shift, exposing fresh material, which†explains the colour variation previously observed.†Reuters
SummaryMars, not Earth, plays a role in†'refreshing' some near-Earth asteroids.

Mars, not Earth, plays a role in†"refreshing" some near-Earth asteroids, causing the space†rocks to appear redder than meteorites, MIT scientists have†found.†

The gravity of the Red Planet causes the asteroid's†surface material to shift, exposing fresh material, which†explains the colour variation previously observed.†

Richard Binzel, a professor of planetary sciences at†Massachusetts Institute of Technology (MIT) and colleague†Francesca DeMeo calculated the orbits of 60 refreshed†asteroids, and found that 10 per cent of these never cross†Earth's orbit.†

Instead, these asteroids only come close to Mars,†suggesting that the Red Planet can refresh the surfaces of†these asteroids.†

"We don't think Earth is the only major driver anymore,†and it opens our minds to the possibility that there are other†things happening in the solar system causing these asteroids†to be refreshed," said DeMeo.†

The idea that Mars may shake up the surface of an†asteroid is a surprising one: The planet is one-third the size†of Earth, and one-tenth as massive - and therefore exerts a†far weaker gravitational pull on surrounding objects.†

But Mars' position in the solar system places the planet†in close proximity with the asteroid belt, increasing the†chance of close asteroid encounters.†

"Mars is right next to the asteroid belt, and in a way it†gets more opportunity than the Earth does to refresh†asteroids," Binzel said.†

"So that may be a balancing factor," said Binzel.†

DeMeo, who suspected that Mars may have a hand in†altering asteroid surfaces, looked through an asteroid†database created by the International Astronomical Union's†Minor Planet Center.†

The researchers looked at 60 asteroids, mapping out the†orbit of each and determining which orbits had intersected†with those of Earth or Mars.†

DeMeo then calculated the probability, over the last†500,000 years, that an asteroid and either planet would have†intersected, creating a close encounter that could potentially†generate asteroid quakes.†

"Picture Mars and an asteroid going through an†intersection, and sometimes they'll both come through at very†nearly the same time," Binzel said.†

"If they just barely miss each other, that's close enough†for Mars' gravity to tug on (the asteroid) and shake it up. It†ends up being this random process as to how these things†happen, and how often," said Binzel.†

From their calculations, the researchers found that 10†per cent of their sample of asteroids only cross Mars' orbit,†and not Earth's.

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