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.MUNRO AMERICAN SPORT JOLIE DARK BROWN PATENT LEATHER LOAFERS WOMEN SZ 9 N ld , AHNU Women 9.5 Merlot Leather Suede Mary Jane Casual Slip On Active Shoes 2311 , KEEN XT 1005 Clogs Closed Toe Women's Size US 8 , BRAND-NEW White Leather - Upper 3 " black Heels SLIDES size 7.5 M by J.G.HOOKSWomen's Dunham 5800BR Size 10EE Waterproof Brown Leather Hiking Walking Shoes K6Natural Soul Fanner Mules - Women's Size 9M Brown , ARRAY Womens kai Leather Closed Toe Mules, Leopard, Size 9.5 9VtBMiu Miu Ballet Flats. Size 36. Comfy! , Wanted Flat Shoes Size 8.5 Yellow GoldROSES & RYE Flat Shoes Leather Beige Size US 7 - Brand New , Marc Fisher Womens Maci Leather Closed Toe Ankle Strap Blue Size 9.0Free People Torrence Ankle Strap Sandals Flats Mauve Brown Purple 37/ 7 $78Skazz S33 Women's Mesh Black/Red Dance Shoes 18M (Men's 16M/Women's 13M) , Dr. Scholl's Persue Sneaker - Women's Size 11M Gray , Merrell Women's Black Size 7.5 Performance Footwear , NEW BALANCE 490 V3 SPEED RIDE RUNNING Womens Size 10BNew Mens House Sheepskin Moccasin Slippers with Warm Real Wool Lining UK Sz 7-10**Easy Spirit Punter Athletic Shoes Womens Size 6 WhiteATELJE 71 Black Emery Textured Leather Slip-On Sneakers Shoe Size 8 , NIKE AIR FORCE ONE AF1 '82 Womens Size 8 Running Walking Shoes 315115-501Women's NEW CAFÈNOIR WOMENS ESPADRILLES We Have Won Praise From Customers Flats , Women's Sperry Suede Flats Loafers 8 Fine Workmanship FlatsBrooks Womens Speed Varsity Vanguard Running Sneaker Size 6 Capri Breeze NWTPropet Travelactiv Xpress - Navy - Womens , NWB Women’s Ryka Crusade Running Shoe Size 7.5 (US) Purple/Violet/Silver/GreyRider Women's Daytona III Slide Black/Grey Sandals , Women's Nike Free Gym Split Toe - Size 8.5 Yoga Running Athletic EUC , MBT 400284-133 Mahuta Gull Gray Purple Toning Orthotic Sneaker Shoe 41 10-10.5 , Merrell Women’s 6.5 ProTerra VIM Sport Hiking Shoes Aluminum J57254Skechers D'Lites Me Time Athletic Shoes - Women's Size 8.5 - Grey/White
"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."