PARIS - Salty water just below the surface of Mars could hold enough oxygen to support the kind of microbial life that emerged and flourished on Earth billions of years ago, researchers reported Monday (Oct 22).
In some locations, the amount of oxygen available could even keep alive a primitive, multicellular animal such as a sponge, they reported in the journal Nature Geosciences.
"We discovered that brines" - water with high concentrations of salt - "on Mars can contain enough oxygen for microbes to breathe," said lead author Vlada Stamenkovic, a theoretical physicist at the Jet Propulsion Laboratory in California.
"This fully revolutionises our understanding of the potential for life on Mars, today and in the past," he told AFP.
Up to now, it had been assumed that the trace amounts of oxygen on Mars were insufficient to sustain even microbial life.
"We never thought that oxygen could play a role for life on Mars due to its rarity in the atmosphere, about 0.14 per cent," Stamenkovic said.
By comparison, the life-giving gas makes up 21 per cent of the air we breathe.
On Earth, aerobic - that is, oxygen breathing - life forms evolved together with photosynthesis, which converts CO2 into O2. The gas played a critical role in the emergence of complex life, notable after the so-called Great Oxygenation Event some 2.35 billion years ago.
But our planet also harbours microbes - at the bottom of the ocean, in boiling hot springs - that subsist in environments deprived of oxygen.
"That's why - whenever we thought of life on Mars - we studied the potential for anaerobic life," Stamenkovic.
LIFE ON MARS?
The new study began with the discovery by Nasa's Curiosity Mars rover of manganese oxides, which are chemical compounds that can only be produced with a lot of oxygen.
Curiosity, along with Mars orbiters, also established the presence of brine deposits, with notable variations in the elements they contained.
A high salt content allows for water to remain liquid - a necessary condition for oxygen to be dissolved - at much lower temperatures, making brines a happy place for microbes.
Depending on the region, season and time of day, temperatures on the Red Planet can vary between minus 195 and 20 deg C.
The researchers devised a first model to describe how oxygen dissolves in salty water at temperatures below freezing.
A second model estimated climate changes on Mars over the last 20 million years, and over the next 10 million years.
Taken together, the calculations showed which regions on the Red Planet are most likely to produce brine-based oxygen, data that could help determine the placement of future probes.
"Oxygen concentrations (on Mars) are orders of magnitude" - several hundred times - "greater than needed by aerobic, or oxygen-breathing - microbes," the study concluded.Jodhpuri New Indian Traditional Leather Pom Womens Ethnic Casual Ladies jutti , Iron Fist Hellwaiin Holiday Women's Tropical Flatform Platform Sandal Shoes - 6Pierre Dumas Womens Shoes NEW $42 Tara Nude Beige Ballet Flat 8 M , G.H. Bass & Co. Sheela B Women's Dark Brown Clog 6.5MBCBGeneration Beckie Women's Veridian Ballet Flat 8.5M , PW MINOR brown leather SOFIA Mary Jane comfort cushion insole walking shoes 7Juicy Couture Size 9.5 Burgundy Fringe suede flats made in Italy gold logo bowSeven7 Cape Verde Women's Espadrille Flats Tan Size 6 NIB Ships N 24h , Klogs Black Leather Mary Jane's, 8.5M...Great Condition!Autumn new women single shoes leather round flat bottom shoes , Merrell women's shoes sz. 9 Plaza Bandeau" Mary Janes leather suede brown , Weejuns Bass Marietta II Burgundy Leather Shoes Women's Size US 7.5 M LoafersNew Orthofeet Women's Mary Jane BLACK Shoes Sz 6.5M No Insole , Women's Flats Shoe Embroidery Fisherman Female Shoe 2018 Spring SummerDr Martens AirWair Agnes Monk-Strap Loafer, Leather Upper, NewHelly Hansen 9.5 shoes blue pink white women.Very Clean. Worn twice. W Nimble R2 , BASS-ELENA WOMEN LOAFER SZ.10 WOMEN BLACK DRESS SHOES~W12834/BASS-ELENA 018Asics Gel-Kayano 20 Women's Running Shoes Grey/Pink/Neon Green Sz 6.5 , Women Shoes L.L. Bean Walking Running Trail Summer Low Profile Sneaker 9.5VINTAGE 1995 NIKE CROSS TRAINING SHOES OG DEADSTOCK SIZE 6 , Women's Superga Sneaker Excellent Quality Athletic ShoesWomen's Brand new Mk Shoes Complete In Specifications Flats , New Women's Puma Vikky Platform VR Black Suede Sporty Size 9.5 , Women Vans Old Skool True white Skateboarding Shoes Classic Canvas size US*6.5 , Nike Women's Roshe One Winter Running Sneaker , Adidas Originals Mid Attitude Revive Women's Sneakers Size 8.5 , New Balance Women's Fresh Foam Zante v2 Shoes Silver with Black , Converse Women's Chuck Taylor All Star Tweed Shoes Black/Egret (553325F)New DC SHOES ADJS300078 TRASE TX Women's Wine (WIN) Sneakers US Size 7~10Steve Madden Size 8 Black Sneakers New Womens Shoes ,
"Our results do not imply that there is life on Mars," Stamenkovic cautioned. "But they show that the Martian habitability is affected by the potential of dissolved oxygen."