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.2 Color Casual Ankle Strap Zipper Nubuck Closed Round Toe Womens Ballet FlatsTalbots Womens Shoes Size 6 1/2 B Brown MulesWomen's Leather Loafer Casual Flat Shoes Rubber Sole Shoes 6 Burgundy/WineRed , ZARA Women's Platform Plimsolls with Faux Fur (Pink, US 6.5, 7.5/) , A35 Aleaa Ballet Flats 995, Cotton, 7.5 USOluKai Size 7.5 Waialua Mesh Gray Slip On Sneaker Walking Comfort Hiking Canvas'Wanted' brand metallic silver slip on shoes with rhinestone embellishment sz 10Women's Skechers 45703/CHSD Shindigs-Foretress Mules Chocolate Suede , Vaneli Womens Mambo Wedge (B)- Pick SZ/Color.COLE HAAN Brown Leather Black Captoe Flat Size 7.5Aerosoles Womens Ship Board Fashion Sneaker- Pick SZ/Color.Merrell 8.5 Brown Slip-On Shoe Women'sadidas Originals Women's EQT Racing 91, White/White/Turbo Fabric, Size 9.5 , RARE WOMEN DON ED HARDY DESiGNS CLUB SERiES SHOES US 6 LEATHER SNEAKERS , ASICS Women's US 9 Gel-Kayano 15 White Blue Running Jogging Shoes SneakersVANS. "Surf Siders" RATA LO Women's SUEDE & Felt Shoes. BROWN US W 10 10.5 & 11. , Merrell Lazer Air Cushion Brown Leather Hiking Trail Boots Shoes Women's 6.5New! Womens Skechers 12761 Flex Appeal 2.0 Simplistic Black/Turquoise B49Clarks Privo 7.5 sneakers gray pinkWOMENS NIKE LUNAR DUET CLASSIC 10 MAdidas Women's Arkyn Originals Running Shoe , K-Swiss Womens Classic VN Fashion Sneaker- Select SZ/Color. , adidas Womens Tubular Viral Casual Shoes Silver /Clear Granite/White S75907Nike Roshe One White & Black Women SZ 6 - 12Life Stride Women's Dreams Wedge , Minnetonka White Mmocassin Shoes SIZE 7.5 , New Balance Women's Sz 11 Salmon Red Fresh Foam 1080 V2 Running Walking ShoesNike Flex Run 2013 2014 Girls (GS) Running Shoes Free Size 4Y , New Balance Womens - White/Blue Walking Shoes Size 6.5 (350897) , Converse All Star Glitter Sneakers in Size 37.5 as seen on Olivia Palermo ,
"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."