NASA’s Curiosity rover has added a new wrinkle to the idea that Mars was once hospitable to alien life. A new chemical analysis of Martian pollution points to past planetary periods when the necessary conditions for life may have been met, but only for a relatively short time. The very processes that led to the formation of elements essential to life in the Martian soil, may have led to the waterless conditions that exist today.
The mobile robot, which has been exploring Mars’ Gale Crater since 2012, analyzed samples of soil and terrestrial rocks as part of an effort to find carbon-rich minerals. Carbon is often seen as essential to life, as its ability to form strong bonds with many other atoms makes molecules such as DNA and RNA possible. The rover’s findings suggest that Mars is not only a hostile environment today, but that any periods in which the planet was habitable may have been brief. However, as the saying goes, life finds a way. More research is needed to determine whether the bacteria may have thrived under more hospitable conditions.
NASA rovers have found evidence that Mars once had abundant organic matter rich in carbon-bearing minerals known as carbonates, and a meteorite of Martian origin has been found to contain carbon, too. To find out which isotopes of carbon and oxygen are present in those carbonates, the Curiosity team turned to the rover’s Sample Analysis on Mars instruments. The equipment heats samples to over 1,650 degrees Fahrenheit (899 Celsius) and uses a laser spectrometer to analyze the gases produced.
When the data was transmitted to Earth, NASA scientists determined that it contained higher levels of certain isotopes of carbon and heavy oxygen than those previously found in Martian samples.
Both elements are important in the carbon cycle, where carbon moves in different ways, thanks to processes such as photosynthesis. The carbon cycle is an important part of life here on Earth, but the researchers found that the proportion of heavy carbon and oxygen isotopes in the samples was much higher than that found on Earth.
As geologists explained in the journal Proceedings of the National Academy of Sciencesthere are actually two ways that soil can become home to this mixture of isotopes. For one, Mars had an alternating series of wet and dry periods. At a later time, the water would have evaporated, bringing lighter versions of those elements up into the atmosphere with it, and leaving the heavier isotopes behind. Because liquid water did not last long, there were brief periods when the planet could be home to life.
On the other hand, carbonates form in highly saline water exposed to extreme cold. It’s not a good place to be if you’re alive, even if you’re an amoeba.
“These formations represent two different climates that may have produced different habitable conditions,” said Jennifer Stern, an astronaut scientist at NASA’s Goddard Space Flight Center, who worked on the paper, in a statement. “Dry cycling would indicate an exchange between habitable and uninhabited environments, while the cryogenic temperatures of the center of Mars would indicate a highly habitable environment where most of the water is locked in ice and unavailable to chemistry or biology. , and what is there is too salty and unpleasant to live.”
Although it may seem backwards to seek Martian life, it is not. David Burtt, a postdoctoral fellow at NASA who led the research, said that although the findings point to a history of great evaporation, life could still find refuge in underground biomes. He also did not rule out the possibility that an even older, more life-friendly atmosphere might have existed before these particular carbonates formed, or that different climates might have existed elsewhere on Mars.
The search for life on Mars has been something of a mixed bag. Although there have been compelling signs, it would be a stretch to call any conclusive evidence. The hunt is on as Curiosity, along with its companion Perseverance, continue their slow journey across the Martian landscape. NASA hopes to send a manned mission to Mars in the 2030s or 2040s, and, if that happens, it would be the first time that living breathing entities have faced the harsh conditions.
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