by The Curiosity Rover Mars he has found interesting chemical evidence, in the form of anomalous amounts of manganese oxide, which shows Mars not only was there a habitable environment billions of years ago, but also an environment inhabited by microbes.
NASA is curious explore the huge crater Gale 154-kilometer (about 96-mile) diameterwhere the rover landed in 2012. Curiosity’s discoveries have already established that the crater was at least partially flooded long ago, although the evidence for this is disputed. However, the rover’s latest findings not only strengthen the argument for an ancient lake, but also suggest that conditions within the lake were favorable for life.
The evidence is related to the compound manganese oxide. Curiosity first discovered small quantities of manganese oxide in Gale Crater in 2016, but now it has found a much greater abundance of manganese oxide in the sedimentary bedrock of a mudstone geological unit called the Murray Formation. The Murray Formation is found on the side of Sharp Hill in the middle of the valley.
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The manganese oxide was identified by Curiosity’s ChemCam instrument, which shines a laser at rocks that scientists want to study. The laser heats a small patch of rock surface, thereby vaporizing it, creating a small cloud of plasma that can be studied from afar by a camera and spectrometer on board ChemCam to determine the composition of the inclined material . ChemCam found mudstone enriched in manganese oxide by up to 45%.
Ar World, manganese oxide is commonly found in lake beds or river deltas where there are high oxidizing conditions. In addition, the microbes present in these environments are able to help catalyze the oxidation process.
Normally, this process requires a steady stream of oxygen, which is scarce on Mars. It is possible that the small amounts of manganese oxide found previously were found on Mars in 2016 explained without significant quantities of oxygen, but the large numbers found in the Murray Formation are another matter entirely. To achieve such an abundance, a significant amount of oxygen would be required for the oxidation process.
“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 coastal deposit,” said lead researcher Patrick Gasda of Los Alamos National Laboratory in a. statement. “On Mars, we have no evidence of life, and the mechanism for producing oxygen in the ancient atmosphere of Mars is not clear, so how the manganese oxide formed and concentrated here is very interesting.”
One clue lies in the nature of the mudstone sediments in which the manganese oxide was found. The manganese oxide-enriched rocks were found at a location between two geological units in the Murray Formation. One unit is known as Sutton Island and appears to represent sediments laid down at the edge of a lake; the other, called Blunts Point, would be deeper in the lake.
The manganese-oxide-enriched mudstone is coarser, with larger grains than the bedrock elsewhere in the crater where only minor abundances of the compound have been found. This supports the theory that the Mackinton Island/Blunts Point region is the site of an ancient river delta that once emptied into the lake, or a shoreline of the lake, representing sites where larger grain sediments would have been deposited priority. down. The larger grains would help create a more porous bedrock than the fine-grained mudstone seen elsewhere in Gale Crater – a mudstone that is likely much deeper in the lake. This porosity would allow ground water to pass through more easily. The manganese could have seeped out of this groundwater as it passed through the coarse-grained mudstone, the scientists say, so it was concentrated within the rocks. Where the oxygen came from to oxidize it, however, is still a mystery.
“These results point to larger processes occurring in the Martian atmosphere or surface water and show that more work is needed to understand oxidation on Mars,” said Gasda.
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The presence of manganese oxide increases the possibility of microbial life within the lake. Not only can microbes catalyze the oxidation of manganese, but they can also use the many oxidation states of manganese as a source of chemical energy for their metabolism, as microbes do on Earth. In other words, in a way, the abundance of manganese oxide may be indirect biosignature.
“The Gale lake environment, as revealed by these ancient rocks, gives us a window into a habitable environment that looks remarkably like places on Earth today,” said Nina Lanza of Los Alamos, who is the Principal Investigator for ChemCam. “Manganese minerals are common in the shallow, oxic waters found on lakeshores on Earth, and it is remarkable to find such recognizable features on ancient Mars.”
The results were published on May 1st Journal of Geophysical Research: Planets.
