A meteorite that landed in the Moroccan desert 14 months ago has been traced back to Mars.
It's only the fifth time a Martian meteorite landing has been witnessed; and, says University of Alberta researcher Chris Herd, the fact that it was picked up just a few months after landing and wasn't subjected to weathering or contamination on Earth, makes it particularly important.
According to Herd, some 600 million years ago the meteorite started out as a fairly typical volcanic rock on the surface of Mars, but was launched off the planet by the impact of an asteroid.
"Our team matched traces of gases found inside the Tissint meteorite with samples of Mars' atmosphere collected in 1976 by Viking, NASA's Mars lander mission," he says.
"At the instant of that impact with Mars, a shock wave shot through the rock. Cracks and fissures within the rock were sealed instantly by the heat, trapping components of Mars' atmosphere inside, and forming black, glassy spots."
The rock then floated through outer space team for somewhere between 700,000 and one million years - until, in July, 2011, it fell throughthrough Earth's atmosphere.
The Martian weathering involved water, showing water was present on the surface of Mars within the past few hundred million years. But there's no evidence of any life forms.
"Because the Martian rock was subject to such intense heat any water borne microbial life forms that may have existed deep within cracks of the rock would have been destroyed," he says.