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.Naturalsoul /Naturelizer Slip On Casual Shoes Gray/black Sz 7.5 crocodile lookShellys London Womens Abeniel Canvas Round Toe Loafers Gray Size 9.0 5maj , DOLCE by Mojo Moxy Womens Akachi Fabric Closed Toe Slide FlatsVera Wang 7.5 M Simply Vera Womens Shoes Ballet Flats Peep Toe Incisive OchreFergalicious By Fergie Mosley Women's Beige Knitted Ballet Flats US Size 10 MBallerines MISS VIDI Daim Beige T 36 / 36,5 Quasi Neuves , Donald J Pliner Elen Crinkled Patent Leather Platform Loafers. Sz9.5M. Almond. , Earth Origins Tova, Cobalt Blue, Size 10.0 gABuMootsies Tootsies Black Leather Slip On Loafers Mules Heels Shoes 7 M (S454) , GUESS "Gray" - Size 9M Women's Loafers , SAS Free time Tripad Comfort Walking Shoes Mocha Womens 10 Medium NewNew Santoni Italy Dark Gray Velvet Venetian Loafer / Mule 5.5 BSaint + Libertine Fiji Black / White Snake Flat Smoking Slipper Ballet Loafer , Skechers BOBS Womens Beach Bingo - Chitty Chat Sneaker- Select SZ/Color. , Women Winter Rabbit Fur Lined Warm Embroidery Floral Mules Loafer ShoesBibi Lou x Free People Womens Madison Platform Wedge Shoes Silver Size 38 New , Womens Saucony Raptor TR Gray Running Shoes Size 7M (Z22)Womens Grey Skechers 22837 Memory Foam Sneakers Casual Slipons 7 Navy Blue , Ribbon Campus White Leisure Sneaker Chic Shoes Low Top Slice Up Flat Stylish New , naturalizer Finny Wedge Fashion Sneakers 175, Black, 7.5 USNike Vapor 9.5 Tour Tennis Sneakers Size 10 Purple Black Wht Women's 631475-005 , NEW BALANCE 580v2 Womens sz 9 Athletic Running Shoes Silver Gray Turqoise Blue , Skechers SKCH 3+ Womens US Sz 7.5 Hidden Wedge Ankle Sneaker BootsSalewa WS Wildfire Vent Womens 7.5 Green Hiking Trail Shoes HSkechers 22769 Sport Womens Gratis Optimist Fashion Sneaker- Choose SZ/Color.Saucony Progrid Mirage 2 Running Women's Shoes Size 5 , Pearl Izumi Womens EM Road N 1 V2 Gray & Blue Athletic Bike Shoes Sz US 6 , NIKE Lunarlon Ladies Running Neutral Ride Soft Running Shoe 7.5 US , Nike Air Prestige Womens Basketball Shoes White Grape Size 9 318972 107Columbia Womens Ventrailia Razor Trail Shoe Oyster Zour Size 11 B US ,
"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."