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EDMONTON — New research suggests Mars’ moons were once part of the planet, blasted into space by some cataclysmic collision long ago.

Until now, the most common theory was that Deimos and Phobos were once asteroids, captured into orbit by Mars’ gravitational field.

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“They kind of look like asteroids,” said Chris Herd, a planetary geologist at the University of Alberta and a co-author of a new paper published in the Journal of Geophysical Research.

“They’re really pockmarked with craters and they have those characteristics that make them look like asteroids we’ve seen farther out.”

Still, doubts remained — especially since the red planet’s two moons are so black.

“Those objects are really dark,” Herd said.

“They absorb most of the light, with the exception of a few per cent of the sunlight that comes in. That means the information you have for figuring what they’re made of is limited.”

Herd and his colleagues took a new approach.