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.Max Rave Silver/Gray Ballet Flats with Buckle Size 8 , Jasmin Zipper Ankle Boots 2 3/4 inch heel 6 M , Fred Perry Moore Linen Canvas leather shoes / Ivory, women UK5 US7 EU38 JP24MERRELL LEATHER/SUEDE MARY JANES.......SIZE: 7.5.......EXCELLENT CONDITION , Steve Madden Women's Grey Slip On Round Toe Ballet Flats US Size 8.5 MPantanetti emerald green made in Italy leather loafers flats US 7 GUC , Born Beige Leather Bow tie flats Slip On Womens Size 7 , naturalizer Saturday Logo Loafers 666, Red Pepper, 8 US , Sam Edelman Circus Cruz Slip On Snake Print Shoes Women's Size 8.5Fossil Turquoise And Silver Shoes Size 6.5 FlatsKlogs Duncan Polyurethane Clogs Display Model Shoes Rural Green Dragonfly 9 M , Women's striped Keds flats size 9 , **Easy Street Elliot Mules - Women's Size 9 M, Pewter Croc , LA Gear Womens Size 7.5 Brown & Pink Athletic Shoes Excellent ConditionNEW Swissies Womens Sz 41 / 9.5 Navy Blue Brushed Leather Tie Up Oxfords Flats , Noble Women's Crystal Rhinestone Flat Square Toe Slip On Oxfords Formal Shoes , Nike ACE 418368-171 White & Gold Soft Spike Golf Shoes Size US 7.5 7 1/2 Women's , New Steve Madden Mens Psailor Grey Moccasin Slippers Size 7 (33937) , MERRELL Women's Siren Sport Trail Hiking Shoes Size 6 US 36 EU Elephant PinkWomen's Luichiny heels size 10 Elegant And Sturdy Package Athletic Shoes , Women's Ll Bean Shoes8.5 M Cheap Flats , adidas Originals Tubular Viral 2 Women's Sesame/Chalk White/White BY9744ASICS T861N 8.5 GEL-FlUX? 5 Wmn's Carbon/Black Mesh/Synthetic Running Shoes , Nike Free RN 2017 Women's Running Shoes (Size 8.5) White Black Punch 880840 102Adidas Breeze AF5345 US Size 6.5 Black - FREE SHIPPING - BRAND NEWNew Nike Womens Air Zoom Pegasus 33 Shield Run Running Shoes 849567-400 Sz 5.5Brooks Ghost 8 Women's 11 Pink Fiery Coral Running Shoes Sneakers Trainers , Womens 6 Merrell Barrado Black Gray shoes sneaker Sport Front Zip Leather flat , Nike Dunk Low Skateboard Shoes Womens US 11 [309324-145] , ONITSUKA TIGER ASICS GEL-FORTIUS TR Athletic Women's Shoes Size 12 ,
"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."