After all, a 4-billion-year-old meteorite from Mars that made a splash here on Earth decades ago contains no evidence of ancient, primitive life on Mars, scientists reported Thursday. In 1996, a NASA-led team announced that organic compounds appeared to have been left behind by living things in the rock. Other scientists have been skeptical, and researchers have broken down that premise over the decades, most recently by a team led by Andrew Steele of the Carnegie Institution for Science.
Small samples of the meteorite show that the carbon-rich compounds are actually the result of water — most likely saline or salt water — flowing over the rock for an extended period of time, 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 millions of years ago. The 4-pound (2 kilogram) rock was found in Antarctica in 1984.
Groundwater moving through the cracks in the rock while it was still on Mars formed the tiny blobs of carbon present, the researchers say. The same could 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 disagreed with these latest findings, calling them “disappointing.”
“While the data presented adds incrementally to our understanding of[the meteorite]the interpretation is hardly new, nor is it supported by the research,” wrote Kathie Thomas-Keprta and Simon Clemett, astromaterial researchers at NASA’s Johnson Space Center in Houston.
“Unsupported speculation does not solve the mystery surrounding the origin of organic matter” in the meteorite, they added.
According to Steele, technological advances made his team’s new findings possible.
He praised the measurements taken by the original researchers, noting that their life-ending hypothesis was “a reasonable interpretation” at the time. He said he and his team – which included NASA, German and British scientists – took care to present their results “for what they are, which is a very exciting discovery about Mars and not a study to disprove the original premise.
This finding “is huge for our understanding of how life began on this planet and helps refine the techniques we need to find life elsewhere on Mars, or Enceladus and Europa,” Steele said in an email. , referring to the moons of Saturn and Jupiter with subterranean oceans .
The only way to prove whether Mars ever had or still has microbial life, according to Steele, is to bring samples to Earth for analysis. NASA’s Perseverance Mars rover has already collected six samples for return to Earth in a decade or so; three dozen samples are desired.
Millions of years after straying through space, the meteorite landed on an ice field in Antarctica thousands of years ago. The small gray-green fragment gets its name – Allan Hills 84001 – from the hills where it was found.
Just this week, a piece of this meteorite was used in a unique experiment aboard the International Space Station. A mini scanning electron microscope examined the sample; Thomas-Keprta operates it remotely from Houston. Researchers hope to use the microscope to analyze geological samples in space — one day on the moon, for example — and debris that could ruin station equipment or endanger astronauts.
