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.Apex A730 Donna Women's Black Double Velcro Slip On Shoe 7/7.5XWAerosoles Womens Hey Girl Silver Metallic Pointy Toe Flats Shoes 7.5 8 BHFO 1007Marc Fisher New Womens Beyond Pewter Leather Flats 7 M Shoes , B.O.C. Born Concepts Margaret Slip-On Comfort Clogs 882, Dark Brown, 7.5 US /ZIGINY, ANNIE BALLERINA FLAT, WOMEN'S, BLACK, US SIZE 6.5 M, SUEDE, NEW/DISPLAYNEW Womens KENNETH COLE Slip On Black Keena Loafer Shoes Size 7.5Ara Womens Slip on Ballet Flat Suede Shoes sz 8SKECHERS Bobs Women's Pureflex 2 Knit Knack Grey/White Slip On Shoes - 7 NWOB , Sperry Top-Sider Bahama Navy Whale Women Size 12M NIB Boat ShoeWomens Shoes/Sneakers Sperry Top Sider Sz 6 M Leather Excellent Barely Worn , Brooks Adrenaline GTS 16 Running Shoes - Women's Size 9 2E, Grey/Turquoise , Asics Womens US 8 Gel-Flux 4 Running Shoes Pink Silver T764N , Skechers Shape Ups Women's Size 8.5 / 38.5 Blue Silver ShoesVANS Authentic (Pool Vibes) African Violet Pineapple Dog Ice Cream WOMEN'S 10Nike Women Tiempo Rio III FG Soccer Cleats Womens Sz 9.5 EUC , ZUMBA FLEX II Purple Shoes *PIK 5 or 5.5 * NIB neon orange z-slide dance , WOMEN'S NIKE FREE RN 2017 LE RUNNING SHOES SIZE 5, NWB 883283 100 $100 , Ahnu Womens Montara II Waterproof Athletic Hiking Trail Running Shoes Size 8 , Skechers 22591 Sport Womens Dreamchaser Ante Up Walking Shoe- Choose SZ/Color.Nike Kawa Slide Womens Style : 834588 BLACK/VIVID PINK Womens Size 5NIKE Women's Free 5.0 TR Fit 5 BRTHE - Size 10.5 US , NIKE Metcon Repper DSX Black/White Running/Training Shoes 902173-007 NEW All Szs , Skechers Shape Ups 2.0 Black Leather Memory Foam Walking Shoes Women's Size 9Crocs Women's Swiftwater Slide Sandal Smoke/White Comfort Shoes , Reebok Z Dual Rush 2.0 Women's Shoes , Adidas Women's Lifestyle Casual Shoes / Fashion 103785 Missy Bassline Size: 8.5429632 102 NIKE AIR FLEX TRAINER Athletic Running Training ShoesSkechers Women's Breathe-Easy-HARMONIA 23097 Natural Brand NewSkechers Women's You - Inspire Ankle-High Walking Shoe , Baskets Femme samples shoes ETNIES THE DEZ BLACK WHITE WOMEN ,
"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."