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Modern Mars could be more hospitable than previously thought.
One study suggests that salt water on the surface of the red planet or near it could contain enough dissolved O2 to support the oxygen-breathing microbes and more complex organisms such as sponges.
"Nobody thought of Mars as a place where aerobic respiration would work, because there is so little oxygen in the atmosphere," said Vlada Stamenkovic, earth and planet scientist at Jet Propulsion Laboratory. "What we are saying is that it is possible that this planet so different from the Earth could have given a chance to aerobic life."
As part of this report, Stamenkovic and his coauthors also identified areas of Mars most likely to contain brine containing the most dissolved oxygen. This could help NASA and other space agencies plan where to send landing gear for future missions, they said.
The work was published Oct. 22 in Nature Geoscience.
On its surface, Mars is not what you would consider a hospitable place for most earthlings.
Here on Earth, 21% of our atmosphere is made up of oxygen – thanks to the abundance of plants and other organisms that create oxygen as a byproduct of photosynthesis .
The Martian atmosphere, meanwhile, contains only 0.145% oxygen, according to data collected by the Martian rovers.
In the absence of plants producing O2, the minute amount of oxygen on Mars is created when solar radiation interacts with CO2 in the atmosphere of the planet.
In addition, the atmosphere of Mars is extremely thin – 160 times thinner than Earth's. In addition, the temperature at the surface frequently drops to minus 100, which makes it extremely difficult for liquid water to be present on the surface of the planet.
Liquid pure water would freeze or evaporate on Mars, but salt water, or brines, could remain in liquid form on the surface of the planet or just below, said the authors. This is because water mixed with salts has a lower freezing temperature than ordinary water. (This is why unhappy people who live in cold climates use salt to melt ice on their sidewalks.)
In the first part of the article, the authors use computer models to show that water mixed with salts already present on Mars could be stable in the liquid state at or near the surface.
Once the authors were convinced that these liquid brines could exist, it was then necessary to determine how much dissolved oxygen could be absorbed by the atmosphere.
"If there are brines on Mars, then oxygen will have no choice but to infiltrate them," said Woody Fischer, a geobiologist at Caltech, who participated in the event. # 39; study. "The oxygen would make it everywhere."
To calculate the amount of oxygen that the brines could absorb, the researchers had to take into account their chemical composition, as well as temperature and atmospheric pressure on the surface of Mars. Brines will absorb more oxygen when the temperature is low and the atmospheric pressure is higher.
Their results showed that the modern planet could withstand liquid environments with enough dissolved O2 to support the oxygen – breathing microbes across the planet. They also found that oxygen concentrations would be particularly high in brines found in the polar regions, where temperatures are cooler.
Until now, this work has been done by computer modeling. But experts still said the study seemed robust.
"The best studies that rely on models to get their results in depth analyze the variables that can influence the results of the model," said Kathleen Mandt, a global biologist at the University of Applied Physics Laboratory. Johns Hopkins University. "This study does a good job of exploring a range of possible outcomes."
However, the study does not prove that there are indeed brines on Mars.
"What we do know is that in theory, there should be brine on Mars and that they would be able to dissolve enough oxygen to be biologically useful," he said. Stamenkovic.
The next step, he said, is twofold.
He hopes that researchers on Earth will experiment to put oxygen-scavenging microbes in brines likely to form on Mars in order to determine the type of chemistry they manufacture and if they can flourish. . The other step would be to send a lander on Mars capable of searching for brines in the underwater depths.
"NASA has done a remarkable job looking for evidence of past living environments," he said. "I am a big proponent of finding livable living environments today, and we can do this by starting to explore whether there is liquid water on Mars."
To this end, Stamenkovic is working on the development of a new tool, no bigger than a shoebox, that could be used to find water on Mars and determine its salinity, without having to dig .
He calls it TH2OR.
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