We already know that water has existed on the surface of Mars but for how long? Curiosity has been searching for evidence for the long term presence of water on Mars and now, a team of researchers think they have found it. The rover has been exploring the Gale Crater and found it contains high concentrations of Manganese. The mineral doesn’t form easily on Mars so the team think it may have formed as deposits in an ancient lake. It is interesting too that life on Earth helps the formation of Manganese so its presence on Mars is a mystery.
The Mars Curiosity Rover was launched in November 2011. It arrived on 6 August 2012 in the Gale Crater region of Mars. It’s purpose was to explore the geology of the area, climatic conditions and the potential for habitability for future explorers. We have seen stunning images from the surface of Mars thanks to Curiosity and our understanding of Mars both past and present has been improved as a result of its work.
A paper published in the Journal of Geophysical Research : Planets has reported on findings using the ChemCam instrument on board Curiosity. The paper’s lead author Patrick Gasda from the Los Alamos National Laboratory’s Space Science and Application group announced the findings of high levels of manganese in rocks from the base of the crater. It is thought that the Gale Crater is an ancient lake so this poses interesting questions as to its origin.
On Earth, biological processes are fundamental to the formation of materials like manganese oxide with photosynthesis producing atmospheric oxygen. There are also microbes that act as a catalyst to the oxidisation of manganese. The problem is that there is no such sign other life on Mars so the process that led to the formation of oxygen in the ancient Martian atmosphere is unclear. If we cannot understand the formation of oxygen, then we struggle to understand how manganese oxide might form. Perhaps something relating to large bodies of surface water could be responsible.
The ChemCam instrument on Curiosity uses a laser to generate small amounts of plasma on the surface of Martian rocks. Light is then collected to enable the composition of the rock to be identified. The team studied sand, silts and muds, the former being more porous than the latter. The majority of the manganese found in the sands is thought to have been the result of ground water percolation. On Earth the manganese is oxidised by atmospheric oxygen in a process that is accelerated by microbes.
We still don’t have all the answers but but the study has revealed yet again, to an environment that was once suitable for life. That environment seems similar to many places on Earth that also display rich manganese deposits.
Full Research Article “Manganese-Rich Sandstones as an Indicator of Ancient Oxic Lake Water Conditions in Gale Crater, Mars”
Abstract
Manganese has been observed on Mars by the NASA Curiosity rover in a variety of contexts and is an important indicator of redox processes in hydrologic systems on Earth. Within the Murray formation, an ancient primarily fine-grained lacustrine sedimentary deposit in Gale crater, Mars, have observed up to 45× enrichment in manganese and up to 1.5× enrichment in iron within coarser grained bedrock targets compared to the mean Murray sediment composition. This enrichment in manganese coincides with the transition between two stratigraphic units within the Murray: Sutton Island, interpreted as a lake margin environment, and Blunts Point, interpreted as a lake environment. On Earth, lacustrine environments are common locations of manganese precipitation due to highly oxidizing conditions in the lakes. Here, we explore three mechanisms for ferromanganese oxide precipitation at this location: authigenic precipitation from lake water along a lake shore, authigenic precipitation from reduced groundwater discharging through porous sands along a lake shore, and early diagenetic precipitation from groundwater through porous sands. All three scenarios require highly oxidizing conditions and we discuss oxidants that may be responsible for the oxidation and precipitation of manganese oxides. This work has important implications for the habitability of Mars to microbes that could have used Mn redox reactions, owing to its multiple redox states, as an energy source for metabolism.
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