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.Soft Style By Hush Puppies Cahill Womens Dark Grey Faux Flats , Ladies shoes loafers size 8 W NIB brown , Women’s Dr. Scholl’s Flats Shoes, Size 8.5W , Fabulous COLE HAAN SLIP-ON LOW engineer style SHOES RUSTIC MULES 7.5 , SKECHERS Women's Size 7.5 M Dark Brown Nubuck Leather Lug-Soled Casual Oxfords , Women's Eddie Bauer Mary Jane Shoes Flats Size 10 M Suede BeigeNEW NINE WEST RED LEATHER OXFORD SHOES HEELS BRAZIL 5.5Skechers Memory Fur navy blue slip ons - womens 10, euro 40SAS Wink Pewter Penny Loafers Flats 7 1/2 7.5 S Slim Slip On Shoes Metalic Moc$80 VINCE CAMUTO CAILEE SUNDANCE SADDLE SOFT NAPPA SILK LEATHER BALLET FLATS , Womens Grace Wedding Bridal Flats Pearls Pumps Rhinestones Shoes Slip on LoafersCLARKS Collection Women's Brown Leather Zip Loafers Booties Shoes Size 10 M , NAOT BROWN BRONZE LEATHER WEDGES CAP TOE SLIP ON LOAFERS SHOES WOMEN'S 40 L 9Born Sz 8.5 Dual Tone Brown Leather Monk Strap Slip On Loafers Womens Size 8.5DANSKO BURGUNDY SLIP ON CLOGS WALKING SHOES SZ 8.5/9Women's Ryka Advance Sport Walker walking shoes - white/blue - size 7 K24111WWLDSkechers Performance Women’s Go Walk 3 Reboot Slip-On Shoe- Size 9 1/2 , New Women'S RUNNING TRAINERS WALKING SHOCK ABSORBING SPORTS FASHION SHOES , Kelsi Dagger Brooklyn KDB Yelle flat Leather Ankle Wrap Pointy-Toed Grey Sz 10 , Womens Tassels Flats Patent Leather British Style Pull on Shoes Classic New , Men's CHAPS CH882 Brown Slip On SlippersW/ memory foam size M 8-9Adidas Adiprene Women Running Athletic Gym Sneakers Turquoise & Gray Sz 10Easy Street Womens Barbara Low Top Slip On Fashion, White flower, Size 12.0 sj4A , Skechers Shape Ups Fitness Womens Athletic Shoes Size 8.5M Exercise work walkingWomen's Nike Free RN 2017 Running Shoes - White/Black/Platinum - NIB!Women's New Balance 1540V2 White with Teal Blue Accents US 10.5 , BOUTIQUE 9 MIRABELLE Burgundy Suede Designer Pumps Heels 7.0 M , adidas Women's Questar Ride Running ShoeLA Gear Ladies T-Raww Mesh Casual LA13R627K-3 Black Grey Womens US size 8Women's Under Armour 1285498001 Micro G Speed Swift 2 Shoes Black
"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."