A four billion-year-old meteorite from Mars that caused a splash here on Earth decades ago contains no evidence of ancient, primitive Martian life after all, scientists have said.
In 1996, a Nasa-led team announced that organic compounds in the rock appeared to have been left by living creatures. Other scientists were skeptical and researchers chipped away at that premise over the decades, most recently by a team led by the Carnegie Institution for Science’s Andrew Steele.
Tiny samples from the meteorite show the carbon-rich compounds are actually the result of water – most likely salty or briny water – flowing over the rock for a prolonged period, Steele said. The findings appear in the Science journal.
During Mars’ wet and early past, at least two impacts occurred near the rock, heating the planet’s surrounding surface, before a third impact bounced it off the red planet and into space millions of years ago. The 4lb (2kg) rock was found in Antarctica in 1984.
Groundwater moving through the cracks in the rock, while it was still on Mars, formed the tiny globs of carbon that are present, according to the researchers. The same thing can happen on Earth and could help explain the presence of methane in Mars’ atmosphere, they said.