A new study led by Kaushik Mitra, from the University of Washington, in the United States, suggests that the presence of manganese oxides on Mars could be a kind of “false alarm” of the possible oxygen in the atmosphere of the planet in the past. In the study, he and the other authors showed that, under conditions on the Red Planet, manganese oxides can be formed without oxygen.
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The Earth is covered by an atmosphere rich in oxygen, which, in addition to serving as the basis for life as we know it, is an important ingredient for reactions with other elements: oxygen can form iron and manganese oxides, present in the Earth’s crust — this The latter oxide, specifically, was found on the Red Planet by the Curiosity and Endeavor rovers.
Scientists interpreted the findings as “clues” from Mars’ primordial atmosphere, which suggested the planet had oxygen in its atmosphere in the past and even water on the surface. However, the new study revealed a new way to produce the oxide without the need for oxygen, which suggests that the element in the atmosphere may not have been necessary for the formation of the identified oxide.
Through reaction chambers that simulated the acidic fluids that occurred on Mars in the past, the researchers discovered that reactions with oxygen atoms linked to some element of the halogen group, such as bromine or chlorine, can also produce manganese oxides — and, they even do it faster than atmospheric oxygen.
While oxygen can react with manganese to form oxides on Earth, it’s unclear whether the same process could happen on Mars. To find out, the team performed the experiments in the chambers and found that chlorate, a compound quite abundant on Mars, did not produce manganese oxides within the timeframe of the experiments.
Bromate, also frequent on Mars, formed the compound in an interval of 6 to 8 weeks; in acidic conditions, it produced oxides hundreds of times faster than oxygen. Therefore, the findings suggest that manganese oxides from Mars may not have signaled the presence of atmospheric oxygen in the past, but more studies are needed for researchers to understand how these minerals formed.
While chlorate is present on Mars, it didn’t produce manganese oxide as quickly — bromate did much faster, but the authors point out that it’s unclear where this compound could have formed there. “There are many possible paths, and Earth and Mars are not identical,” explained Nina Lanza, a researcher who was not involved in the new study. “We need to think about this very broadly, and because of this really strong tie between life and manganese minerals, it’s a really important answerable question,” she said.
The article with the findings was published in the journal Nature Geoscience.
Source: Nature Geoscience; Via: EOS