• Results provide evidence for long and varied history of water in Mars Gale Crater• Sulphur and iron rich groundwater in Gale Crater was habitable by Earth standards• Mudstones in Gale Crater close in composition to rocks in Watchet Bay in North Devon, highlighting a terrestrial analogue

Newswise — Mineral veins found in Mars's Gale Crater were formed by the evaporation of ancient Martian lakes, a new study has shown.

The research, by Mars Science Laboratory Participating Scientists at The Open University and the University of Leicester, used the Mars Curiosity rover to explore Yellowknife Bay in Gale Crater on Mars, examining the mineralogy of veins that were paths for groundwater in mudstones.

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!

"However as Dr Schwenzer from The Open University concludes, some microbes on Earth do like sulphur and iron rich fluids, because they can use those two elements to gain energy. Therefore, for the question of habitability at Gale Crater the taste of the water is very exciting news."

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.

The study predicts the original precipitate was likely gypsum, which dehydrated during the lake's burial.

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.

The mudstones with sulphate veins in the Gale Crater were also found to be close in composition to rocks in Watchet Bay in North Devon, highlighting a terrestrial analogue which supports the model of dissolution of a mixed silica and sulphate-rich shallow horizon to form pure sulphate veins.

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."

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The paper, 'Fluids during diagenesis and sulphate vein formation in sediments at Gale crater, Mars', published in Meteoritics & Planetary Science by Schwenzer et al. is available here: http://www.onlinelibrary.wiley.com/doi/10.1111/maps.12668/abstract;jsessionid=C356059B3DF8928987AC75CBEB53FC03.f04t01

Notes to editors:

For more information contact Dr Susanne Schwenzer from The Open University on [email protected] or Professor John Bridges from the University of Leicester on [email protected]

About The Open University

The Open University (OU) is the largest academic institution in the UK and a world leader in flexible distance learning. Since it began in 1969, the OU has taught more than 1.8 million students and has almost 180,000 current students, including more than 15,000 overseas.

Over 70% of students are in full-time or part-time employment, and four out of five FTSE 100 companies have sponsored staff to take OU courses.

Space Science at The Open University

Space Science is one of The Open University's Key Strategic Research Areas. OU research into space contributes to major global challenges through scientific exploitation of imaging and detection technologies and to building the Space sector of the UK economy. For further information please visit: http://www.open.ac.uk/research/main/our-research/space

About the University of Leicester

The University of Leicester is led by discovery and innovation - an international centre for excellence renowned for research, teaching and broadening access to higher education. The University of Leicester is ranked among the top one per cent of universities in the world by the THE World University Rankings and also among the top 100 leading international universities in the world. It is among the top 25 universities in the Times Higher Education REF Research Power rankings with 75% of research adjudged to be internationally excellent with wide-ranging impacts on society, health, culture, and the environment.

Find out more: https://www.le.ac.uk/about-us

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Newswise: Veins on Mars Were Formed by Evaporating Ancient Lakes

Credit: University of Leicester/Open University

Caption: Sulfate veins prominent at Darwin outcrop veins, observed on sol 402, NavCam NRB_432923862. Field of view 1.3 m. B) Garden City image, observed on sol 924, MastCam ML004061. White sulfate veins cut through the surrounding sediments. Scale bars are 1 m.

Newswise: Veins on Mars Were Formed by Evaporating Ancient Lakes

Credit: University of Leicester/Open University

Caption: 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 2 cm (NASA image PIA16815_Fig 1_WB_unannotated-full).

Newswise: Veins on Mars Were Formed by Evaporating Ancient Lakes

Credit: University of Leicester/Open University

Caption: Watchet Bay cliff outcrops on the N. Somerset coast, UK (51°10?59?N, 3°20?10.7?W). 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. [12]). 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 30 m. Scale bar is 1 m. 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 0.5 m. C) Pure gypsum veins (some with orange coloration) in gray mudstone member of Watchet Triassic mudstone. Scale bar is 0.25 m.

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Meteoritics & Planetary Science