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.Women Casual White Sneakers Pu Leather Platform Creepers Pumky Student Shoes , Aerosoles Womens Great Plush Wedge Sandal, Turquoise, 6 M US Sale , Trotters women shoes woven loafers leather blue size 6 Slim Brazil , Bass Nature Clogs Mules Womens Sz 7 M Black Leather Slides Slip On Shoes NICE**Dr. Scholl's Luna Slip On - Women's Size 8.5M, Greige , Born Hand Crafted W31794 Black Leather Split Toe Mary Jane Shoes Women's 7 / 38 , WOMEN'S SUEDE COMFORT MAVENS BY MERCY FLATS SZ / 8 1/2Sperry Top Sider Women's Shoes slip ons 7.5M leopard sparkle glitter leatherCalvin Klein Womens Fiana Leather Cap Toe Ballet Flats, Soft White, Size 6.0 LKfKenneth Cole New York Women's Wade Strap Detail Velvet Indigo/Black Size 8.5WOMENS NIKE DART 7 SIZE 7 RUNNING SHOES VGPC , New Womens Reebok speedlux 2.0 athletic shoes Running On Sale , New Fashion womens casual round toe cross strap flats star moon decor Cute , Rebecca Minkoff Vicky Black Womens Shoes Size 9.5 M Flats MSRP $150Asics GT 2000 v 3 Women's Running Shoes Lightning/Hot Pink/Navy T551N(D) Sz 11Soft Furry Fluff Warm Comfy Men Winter Slippers Casual Home Indoor Shoes 1114 , CHAUSSURE DE VILLE TOUT EN CUIR MULTICOULEUR "LONDON STYLE " P/40 NEUF/EMBALLEConverse All Star Chuck Taylor Womens Size 6 Black Low Top Sneakers Shoes , Women's Inov 8 Roclite 275 Gore-Tex Trail Running Shoes Size 8 US , Women's $40 Harborsides Flex-a-Lite, Blue/Pink, 7 New Product Athletic ShoesUnder Armour SpeedForm Apollo 2 Womens Running Shoes 1266241 913 Teal/Pink , New Converse All Star Graffiti Rose Geometric Metallic Low Cut Women Shoes 10 , New Womens Salewa Fire Vent Shoes Size 8 71F pbSkechers Shape Ups X Wear Hyper Active 8.5 Black Mary Jane Walking Toning Shoes , Vans Half Cab Navy Women's Size: 7.5Women's Adidas Swift Run White/White Size 9.5- CQ2021 , Altra Lone Peak 2.0 Women's US Sz 6 Gaiter Trap Shoes A2453-2 ~ NEW!!New Balance 1296V2 Womens Blue Mesh & Synthetic Athletic Tennis Shoes 10.5 , NIKE WOMENS STAMINA CASUAL 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."