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.BioNatura Women's Sz 39 Red Suede Comfort Sandals Slip On Mule Flower Italy , Merrell Plaza Bandeau Performance Footwear - Black 8M - Mary Janes - Comfortable , BALLERINE FEMME NOIR PETIT NOEUD SEMELLE INTERIEUR CUIR POINTURE 38 , Soda Amity - S Women's Silver Shimmer Loafers / ShoesWomens Danskin Now Pink Slip On Memory Foam Moccasin Style Shoes - Size 6 , Clarks Shoes Women's Loafers Brown Leather Slip On Buckle 1-3/4" Wedge Sz 7 MAnnaKastle Womens Woven Backless Slipper Flat Mule with Bow , Trotters Women's Mila Goldwash Metallic Soft Nappa Leather Loafer 6 W (D)nine west metallic flats size 10 MZee Alexis Women's Stella Woven Slip On Shoe Red 37 US 6.5 , Shoes women adidas size 7 1/2 , Traditional US 6-12 Indian Women Shoes Designer Blue Mojari Ballerinas , Gorgeous Popular Banned UK Punk Rock Skull Print Style Black Ladies Ballet Flats , Audrey Brooke Womens Mojito Leather Closed Toe Ballet Flats, Black, Size 6.0 JHM , $155 COLE HAAN ~MARDI SHEARLING MULE 7.5 B , New Balance 350 Running Athletic Shoes WR350WP Womens Size 7BOfficial DC Comics Superman Slip On Super Soft Slippers - Fits 5-7 VII 7Drew Elite Sneaker Black Leather- Size 6 , MBT The Anti-Shoe Size 9 Brown Leather Rocker Sole Mary Jane Walking Toning Shoe , Salomon Sense Mantra 3 Running Training Shoes Women's Size 8Womens 9 Nike ACG All Conditions Gear Trail Running Shoes Green CampaignSperry Seacoast Womens STS95128 White Casual Sneakers Size 7.5M (S681)KEDS Striped 10 Tribal Canvas Sneakers Tennis Shoes Boho Bohemian African 90sNEW adidas Driver Val Z - Black Golf Shoes (Women's Multiple Sizes)Nike FS Lite Run 3 Women's Running Shoe 807145 010 Size 5 , New Nike Womens Zoom Winflo 5 Run Running Shoes AA7414-600 Sz 7.5 particle rose , Clarks Women's 31092 Tri Amelia Black Combi Sz 6-10 NEWBROOKS ADRENALINE GTS 7 WOMEN'S ATHLETIC RUNNING SHOES 7.5 EUC B21 , Women's Nike Shox 318164-103 Running Shoes Sz 7.5 US , Puma Womens Size 6.5 Basket Classic Gold Black Metal Sneakers 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."