Veins on Mars were formed by evaporating ancient lakes
Mineral veins found in Mars's Gale Crater were formed by the evaporation of ancient Martian lakes, a new study has shown.
The study suggests that the veins formed as the sediments from the ancient lake were buried, heated to about 50 degrees Celsius and corroded.
Professor John Bridges from the University of Leicester Department of Physics and Astronomy said: "The taste of this Martian groundwater would be rather unpleasant, with about 20 times the content of sulphate and sodium than bottled mineral water for instance!
|Drill hole into the John Klein target within Sheepbed Member of Yellowknife Bay, with a light-toned sulfate veinlet visible |
on the back wall. The light-toned veins have been identified as sulfates by ChemCam (Nachon et al. ; Schroeder et al.
) and CheMin (Vaniman et al. ). Drill hole is 1.6 cm diameter. Image is white balanced. Scale bar is 2cm
The researchers suggest that evaporation of ancient lakes in the Yellowknife Bay would have led to the formation of silica and sulphate-rich deposits.
Subsequent dissolution by groundwater of these deposits -- which the team predict are present in the Gale Crater sedimentary succession -- led to the formation of pure sulphate veins within the Yellowknife Bay mudstone.
|Watchet Bay cliff outcrops on the N. Somerset coast, UK (51°10Ļ59ļN, 3°20Ļ10.7ļW). These outcrops consist |
of Upper Triassic sediments from the Mercia Mudstone Group thought to have formed in a mixed floodplain
and playa origin environment (Talbot et al. ). A) This cliff outcrop contains nodular sulfate and clay mixtures
toward the base (arrowed) and pure gypsum veins in the mid part of the cliff. Cliff height 30m. Scale bar is 1m. B)
White gypsum veins derived by partial dissolution of sulfate-rich deposits formed by near-surface evaporation.
SD sandstone dyke, Gy and clay gypsum nodule. Scale bar is 0.5m. C) Pure gypsum veins (some with
orange coloration) in gray mudstone member of Watchet Triassic mudstone. Scale bar is 0.25m
The team compared the Gale Crater waters with fluids modelled for Martian meteorites shergottites, nakhlites and the ancient meteorite ALH 84001, as well as rocks analysed by the Mars Exploration rovers and with terrestrial ground and surface waters.
The aqueous solution present during sediment alteration associated with mineral vein formation at Gale Crater was found to be high in sodium, potassium and silicon, but had low magnesium, iron and aluminium concentrations and had a near neutral to alkaline pH level.
Ashwin Vasavada, Curiosity Project Scientist from the NASA Jet Propulsion Laboratory said: "These result provide further evidence for the long and varied history of water in Gale Crater. Multiple generations of fluids, each with a unique chemistry, must have been present to account for what we find in the rock record today."
The paper published in Meteoritics & Planetary Science.
Source: University of Leicester [August 05, 2016]