A 4 billion-year-old meteorite from Mars that caused a splash on Earth decades ago contains no evidence of ancient, primitive Martian life after all, scientists reported Thursday. 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, the AP reports, 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 journal Science. 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 4-pound 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, researchers said.
The same thing can happen on Earth and could help explain the presence of methane in Mars' atmosphere, they said. But two scientists who took part in the original study took issue with these latest findings, saying they stand by their 1996 observations. Steele said advances in technology made his team's new findings possible. He commended the measurements by the original researchers and noted that their life-claiming hypothesis "was a reasonable interpretation" at the time. He said he and his team took care to present their results “for what they are, which is a very exciting discovery about Mars." (NASA plans to bring rock samples back from Mars for study.)