Curiosity Mars rover He detected intriguing chemical evidence in the form of abnormal amounts of manganese oxide. Anthem Billions of years ago it had not only a habitable environment, but also an environment probably inhabited by microbes.
NASA’s Curiosity Exploring the giant Gale crater with a diameter of 154 kilometers (about 96 miles)Curiosity’s discoveries revealed that the crater was at least partially flooded long ago. evidence for this has been challenged. However, the rover’s latest findings not only strengthen the claim of an ancient lake, but also suggest that the conditions within the lake were conducive to life.
The evidence is associated with the manganese oxide compound. Curiosity first found small amounts of manganese oxide in Gale Crater in 2016, but has now discovered much greater abundances of manganese oxide in the sedimentary bedrock of the mudstone geological unit called the Murray Formation. The Murray Formation is located on the slope of Mount Sharp, in the center of the crater.
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Manganese oxide was identified by Curiosity’s ChemCam instrument, which fired lasers at rocks that scientists wanted to study. The laser heats a small piece of the surface of a rock, thus vaporizing it, resulting in a tiny cloud of plasma that ChemCam’s onboard camera and spectrometer can examine remotely to determine the composition of the cut material. ChemCam discovered mudstone enriched up to 45% in manganese oxide.
Open SoilManganese oxide is often found in lake beds or river deltas where there are highly oxidizing conditions. Additionally, microbes found in these environments can help catalyze the oxidation process.
Usually this process requires a constant flow of oxygen, which is in short supply on Mars. Previously discovered small amounts of manganese oxide may have been found on Mars in 2016. Explained without significant amounts of oxygenbut the large abundances discovered in the Murray Formation are another matter entirely. To achieve such abundances the oxidation process would require significant amounts of oxygen.
“Manganese oxide is difficult to form on the surface of Mars, so we did not expect to find it in such high concentrations in a shoreline deposit,” said principal investigator Patrick Gasda of Los Alamos National Laboratory. expression. “We have no evidence of life on Mars, and the mechanism for producing oxygen in Mars’ ancient atmosphere is unclear, so it’s really puzzling how manganese oxide formed and concentrated there.”
There is a clue in the nature of mudstone sediments where manganese oxide is found. Manganese oxide-rich rocks were found in a location between two geological units in the Murray Formation. The unit is named Sutton Island and appears to represent sediments deposited on the edge of a lake; The other, nicknamed Blunts Point, would be deeper in the lake.
The manganese oxide-enriched mudstone has larger grains and is coarser-grained than the bedrock elsewhere in the crater, where only small amounts of the compound have been discovered. This supports the theory that the Sutton Island/Blunts Point area was either the site of an ancient river delta that once emptied into the lake or was a shoreline of the lake; both represent places where larger-grained sediments are preferentially deposited. down. Larger grains may have contributed to a more porous bedrock than the fine-grained mudstone seen elsewhere in Gale Crater (possibly mudstone from much deeper in the lake). This porosity would allow groundwater to pass more freely. Scientists say that manganese may have leaked from this groundwater as it passed through the coarse-grained mudstone and concentrated in the rocks. But where the oxygen comes from to oxidize it still remains a puzzle.
“These findings point to larger processes occurring on Earth.” atmosphere of mars or surface water, and further studies are needed to understand oxidation on Mars,” Gasda said.
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The presence of manganese oxide also strengthens the possibility that microbial life may exist in the lake. Not only can microbes catalyze the oxidation of manganese, they also have the potential to use the many oxidation states of manganese as a source of chemical energy for their metabolism, as microbes do on Earth. In other words, the abundance of manganese oxide is somewhat of an indirect effect. biosignature.
“The Gale lake environment revealed by these ancient rocks gives us a window into a habitable environment that is surprisingly similar to places on Earth today,” said Nina Lanza of Los Alamos, ChemCam’s Principal Investigator. “Manganese minerals are common in shallow, oxic waters found along lake shores on Earth, and it is remarkable that such recognizable features were found on ancient Mars.”
The findings were published May 1. Journal of Geophysical Research: Planets.