Atmospheric oxygen was not needed to form manganese oxide on ancient Mars

(ORDO NEWS) — When NASA rovers discovered manganese oxides in the rocks of the Gale and Endeavor craters on Mars in 2014, some scientists speculated that there might have been more oxygen in the Red Planet’s atmosphere billions of years ago.

Using lessons learned from Earth‘s geologic record, scientists have concluded that the presence of manganese oxides indicates that Mars experienced periodic increases in atmospheric oxygen in the past before dropping to today’s levels.

But a new experimental study from Washington University in St. Louis refutes this view.

Scientists have found that under Martian-like conditions, manganese oxides can easily form in the absence of atmospheric oxygen.

Using kinetic modeling, the researchers also showed that the oxidation of manganese is impossible in the carbon dioxide-rich atmosphere that ancient Mars must have had.

Mars is a planet rich in halogens such as chlorine and bromine. “Halogens are found on Mars in forms different from those on Earth, and in much greater quantities.

We hypothesized that they would be important for the fate of manganese,” the researchers said.

The scientists conducted laboratory experiments using chlorate and bromate to oxidize manganese in water samples, replicating the fluids that existed on the surface of Mars in the ancient past.

The researchers found that halogens convert dissolved manganese in water into manganese oxide minerals thousands of times faster than oxygen.

In addition, under the slightly acidic conditions that scientists believe existed on the surface of early Mars, bromate produces manganese oxide minerals faster than any other available oxidizing agent.

Under many of these conditions, oxygen is completely incapable of forming manganese oxides.

The new results change the underlying interpretations of the habitability of early Mars.

But just because there was probably no oxygen in the atmosphere in the past, there is little reason to believe there was no life there, the scientists said.

“Even on Earth, there are several life forms that do not require oxygen to survive,” the researchers say.

“We need more experiments under various geochemical conditions that are more suited to specific planets such as Mars, Venus, and ocean worlds such as Europa and Enceladus, in order to have a correct and complete understanding of the geochemical and geological environment on these planetary bodies.

Each planet is unique in itself, and we cannot extrapolate observations made on one planet to accurately understand another planet.”


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