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.NINE WEST Marie Light Beige Tan Suede Leather Flat Ballet Slip On Size 7 $80Sperry Top-Sider black SHOES WOMENS SIZE 7 1/2 M , Elegant Tassel Womens Ladys Blocks Leather Loafers Brogue Slip on Girl's SHoes , David Tate Carson Women's Black Glazed Buffalo Casual Moccasins 8M , LifeStride Women's Ballad Slip-On Loafer, Black, Size 8.0 U1U5NEW Women's Soft Spots Constance Bone Leather Casual Slip on Comfort Shoe , Sperry Top-Sider Women's Intrepid Linen Mesh Boat ShoesBruno Magli Womens Shoes Size 5.5 Burgundy Leather Slingback Peep Toe Low Heel , COLE HAAN WOMEN'S HINCKLEY BOOTIES (W00381) BLACK SUEDE 5 MEDIUM $280PRADA BROWN SUEDE BALLET FLATS SIZE 39 US 9Jcrew Womens Pointed Toe Tie Espadrilles Nib Size 8Ballerine MAM'ZELLE chaussure plate femme sneaker sport mocassin CUIR.39.NEUF , Women's KEEN Brown Leather Casual Oxfords US 9Keen Cascade CNX Blue Water Shoe Beach Pool 38.5 8New Balance 101 Heather Grey Pink WL101HG Women's Casual Athletics Shoes 9 40.5 , Ladies Hitec Lightweight Trainers Pajo Women'sDANSKIN NOW SHOES WOMEN'S SIZE : 6 , COOL Fashion Womens Loafers Slip on Leather Casual Leisure Slip on Walking ShoesNaturalizer Womens bengol Almond Toe Slide Flats Black Size 6.0 epROBROOKS Adrenaline GTS 15 Women’s Running Training Shoes Sz 8 Grey Blue YellowBarely Worn, Great Condition, Multi-color, Striped, Men's 6.5 womens 8Merrell Womens 8.5 Continuum Gore-Tex Sport Hiking Boots Shoes Vibram BeigeFILA Women's Memory Resilient Black/White/Silver Cross-Trainers Shoes - 8 Wide , Keen A86 TR Sports Shoes Asymmetrical Sneakers Red Orange 52014 Womens 9 TrailWomen's ballroom dance shoes New Product Athletic Shoes[BS7277] Womens Reebok Ultra 4.0 Les Mills Cardio Sneaker - Black Red WhiteAsics Gel Solution 3 Womens Size 9 White Blue Tennis Shoes D7Women's NIKE LUNAR CONVERGE 852469 White Athletic Sneakers Shoes NEWVANS UNISEX OLD SKOOL METALLIC LEOPARD BLACK SHOES SZ 7 WOMENS / 5.5 MENS NEWBaskets Femme samples shoes ETNIES PLUS NINJA GREEN WHITE WOMEN
"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."