A team led by Lund University in Sweden used neutron and X-ray tomography to investigate a meteorite from Mars. The technology, which will most likely be used when NASA examines samples from Mars in 2030, revealed that the meteorite had only had limited exposure to water, making life at that time and place unlikely.
Mars is now a frigid desert. However, dried up deltas and riverbanks show that water once flowed over the plant’s surface. What happened to everything? Scientists have been trying to find an answer to this question for decades, hoping to understand how Mars became an arid wasteland while Earth retained its water and became a biological paradise.
Now, a team of geologists and atmospheric scientists has created a new picture of Mars’s past by plugging observations of the red planet into new models: Much of the planet’s ancient water may have been trapped in minerals in the crust, where it still exists today.
NASA’s Perseverance spacecraft parachuted onto the dusty surface of Mars in February 2021 in a cloud of smoke. The vehicle will skid around and collect samples for several years in order to answer the question posed by David Bowie in Life on Mars in 1971. Although Nasa does not intend to return the samples to Earth until around 2030, material from Mars is already being studied – in the form of meteorites. In a new study published in Science Advances, an international research team has studied an approximately 1.3 billion-year-old meteorite using advanced scanning.
A more probable explanation is that the reaction took place after small accumulations of underground ice melted during a meteorite impact about 630 million years ago. Of course, that doesn’t mean that life couldn’t have existed in other places on Mars, or that there couldn’t have been life at other times.
Josefin Martell
“Because water is central to the question of whether life ever existed on Mars,” explains Josefin Martell, a geology doctoral student at Lund University, “we wanted to investigate how much of the meteorite reacted with water when it was still part of the Mars bedrock.”
The researchers used neutron and X-ray tomography to answer the question of whether there was any major hydrothermal system, which is generally a favorable environment for life to occur. X-ray tomography is a common method of inspecting an object without causing damage to it. Because neutrons are extremely sensitive to hydrogen, neutron tomography was used.
This means that if a mineral contains hydrogen, it is possible to study it in three dimensions and determine where the hydrogen is located in the meteorite. When scientists study material from Mars, they are always interested in hydrogen (H), because water (H2O) is required for life as we know it. The results show that only a small portion of the sample appears to have reacted with water, implying that the alteration was not caused by a large hydrothermal system.
“A more probable explanation is that the reaction took place after small accumulations of underground ice melted during a meteorite impact about 630 million years ago. Of course, that doesn’t mean that life couldn’t have existed in other places on Mars, or that there couldn’t have been life at other times,” says Josefin Martell.
If the new model is correct, the story of the planet’s adolescence must be rewritten. With all of the water thought to be trapped in the Martian crust today, the planet had far more surface water in its youth than previous models had estimated—and that early epoch may have been even more hospitable to microbial life than previously thought.
“This paper allows for the possibility of a once-blue Mars, even if only for a short time,” says Paul Byrne, a planetary scientist at North Carolina State University who was not involved in the new study.
The researchers hope that the findings of their study will be useful when NASA returns the first samples from Mars around 2030, and there are many reasons to believe that current technology with neutron and X-ray tomography will be useful at that time.
“It would be great if we could study these samples at the European Spallation Source, ESS, in Lund, which will be the world’s most powerful neutron source by then,” Josefin Martell concludes.
