Scientists say a four-billion-year-old meteorite from Mars caused a scattering here on Earth decades ago that contains no evidence of ancient primitive life on Mars.
In 1996, a team led by NASA announced that the organic compounds in the rock had been left by living organisms. Other scientists have been skeptical and researchers have debunked this hypothesis for decades, most recently a team led by Andrew Steele of the Carnegie Institution for Science.
Steele said small samples of the meteorite show that the carbon-rich compounds are actually the result of water — salty or likely salty water — that has been flowing over the rock for a long time. The results appear in the journal Science.
During Mars’ wet period and early past, at least two impacts occurred near the rocks, warming the planet’s surrounding surface, before a third impact bounced off the Red Planet into space millions of years ago. The 4 lb (2 kg) rock was found in Antarctica in 1984.
According to the researchers, the groundwater moving through cracks in the rock, while it was still on the surface of Mars, formed the tiny balls of carbon that are present. They said the same could happen on Earth and could help explain the presence of methane in Mars’ atmosphere.
But two of the scientists who took part in the original study disputed these latest findings, calling them “disappointing.” In a joint email, they said they stand by their 1996 notes.
“While the data presented gradually adds to our (meteor) knowledge, the explanation is not new, and is not supported by research,” wrote Kathy Thomas Kiberta and Simon Klimt, astronomical materials researchers at NASA’s Johnson Space Center in Houston.
They added that “unsupported speculation does nothing to solve the mystery surrounding the origin of the organic matter” in the meteorite.
According to Steele, technological advances made his team’s new discoveries possible.
He praised the measurements made by the original researchers and noted that their alleged hypothesis of life “was a reasonable explanation” at the time. He and his team – which includes NASA scientists and German and British scientists – were interested in presenting their findings “for what they are, a very exciting discovery about Mars and not a study to disprove” the original hypothesis, he said.
Steele said in an email, referring to the subterranean oceans of the moons of Saturn and Jupiter.
According to Steele, the only way to establish whether Mars has microbial life or still exists, is to bring samples back to Earth for analysis. NASA’s persevering spacecraft on Mars has collected six samples to bring back to Earth within a decade or so; Three dozen samples are required.
After millions of years of drifting through space, the meteorite landed on an ice field in Antarctica thousands of years ago. The little gray-green lot got its name, Allan Hills 84001, from the hills in which it was found.
Just this week, a piece of this meteorite was used in a first-of-its-kind experiment aboard the International Space Station. Examination of a small scanning electron microscope of the specimen. The researchers hope to use the microscope to analyze geological samples in space — on the moon one day, for example — and debris that could destroy station equipment or endanger astronauts.