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.New Womens Ladies Diamante Sport Slip On Sneaker Pumps Shoes UK Sizes 3-8 , SAM AND LIBBY (sport) WOMENS MARY JANE SHOES SIZE 10MNaturalizer S60 Brown Croc Leather Adjustable Buckle Chunky Heel Comfort Mule 6M , Bearpaw Womens haven Suede Closed Toe OxfordsClarks 83662 Leather Slip-on Clogs Mule Flats Leather Brown 8.5 M Sandals BucklePuma Tustin Women's Slip On Loafer SZ 10 , Ballet Flats Black Bow Round Toe Scrunch Rubi Leather Look Neutral Soft Pump 37Minnetonka liberty black braided design wrap around sandal SZ 6 NewSam Edelman Circus Womens Shoes BOY BYE Espadrille 6 6.5 7 7.5 8 8.5 Canvas, NewIron Fist Love Me Now Boat Red Tattoo Flat Shoes Slip Sz 6 On NIBNEW Drew womens solid tan Drilex Orthapedic Diabetic mary janes 9.5 M NWOBSAS Women WEAVE Black Leather Moccasin Loafer Flat Shoe 10N 10 Narrow , Clarks Leather Slip-on Shoes - Ashland Lane PICK SIZE , Womens New Balance 715 Running Shoes Size 7.5 B W715GB , Puma Lab II 2 Women's US Size 10 Mint Green Brown White Casual Walking ShoesH&M Womens Sneakers White Black Stripe zebra Size 9.5 Shoes Brand NEW , Women's New Balance Running Navy/White 690 V4 W690HB4 Speed RideWomen's The North Face Trail Hiking Walking Athletic Shoes Gray Silver Black 7.5 , ROCKPORT LADIES CASUAL WALKING SHOES BROWN LEATHER UPPER SIZE 8.5M GREAT COND**Skechers-Go Step Primary Slip On Sneaker, Women's Size 5.5, BlackEmerica The Reynolds Low Vulc Skate Shoe Black/Brown Size 5.5Under Armour 3019918 Womens Threadborne ShiftB(M)- Choose SZ/Color.WMNS AF1 ULTRA FORCE MID JOLI QS (802814 001) SZ 12 (29 CM)Nike Air Huarache Run PRM Black Sail Gum 683818-011 Women's Size 5.5 NWOB , PUMA Roma White Black Sneakers Womens 7.5 Leather Upper Athletic Tennis ShoesNike Womens Lunarconverge Running Shoes Anthracite Grey Hot Punch Pink 852469002Cheeks Easy Shapers Incline Trainer 3.0 White/Lime 6.5 Shoes , New Balance Womens Size 9B () Silver Blue Running Shoes W540SB2SFC Shoes For Crews Aurora White Leather Women's 9143 Size 8 / 38.5 $69 NEWMERRELL SLEET AGILITY CHARGE TRAIL RUNNING SHOES J37720 WOMENS 10.5 GREY YELLOW ,
"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."