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McLaughlin Crater is 90.92 km (56.50 mi) in diameter and 2.2 km (1.4 mi) deep with a floor that is well below Martian “sealevel” and contains clays that bear iron and magnesium as well as carbonate minerals that resulted from ancient water’s action on the rocks within the crater.
The Mars Reconnaissance Orbiter has found evidence that the water came from beneath the surface between 3.7 billion and 4 billion years ago and remained long enough to make carbonate-related clay minerals.
The paper from a group of scientists led by Joseph Michalski from the Planetary Science Institute states:
“Here we present a conceptual model of subsurface habitability of Mars and evaluate evidence for groundwater upwelling in deep basins. Many ancient, deep basins lack evidence for groundwater activity. However, McLaughlin Crater, one of the deepest craters on Mars, contains evidence for Mg–Fe-bearing clays and carbonates that probably formed in an alkaline, groundwater-fed lacustrine setting.”
There has been data collected by the CRISM spectrometer on the MRO, the TES instrument on Mars Global Surveyor and also THEMIS on Mars Odyssey, have all shown deposits of clays and carbonates in the McLaughlin Crater. The minerals formed in an environment much different from the acidic conditions elsewhere on Mars.
“The deposits in McLaughlin Crater could have very high preservation potential for organic materials, in much the same manner as turbidites do on Earth.”
Cyanobacteria, which are common in alkaline lakes on Earth may have aided in the formation of carbonate minerals in lakes such as the McLAughlin Crater on Mars.
Sometimes these bacteria become form microscopic fossils. If similar conditions existed in the craters ancient alkaline lake fossils of micro-organisms may still be there awaiting us.
“This environment strongly contrasts with the acidic, water-limited environments implied by the presence of sulphate deposits that have previously been suggested to form owing to groundwater upwelling.”
Water-made channels which are now dry, appear to flow down the walls of McLaughlin Crater and stop well above the crater floor, which indicates they once provided water to a lake. “The deposits in McLaughlin Crater could have very high preservation potential for organic materials, in much the same manner as turbidites do on Earth.”