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.Me Too Black Leather Animal Print Ballet Flats Womens Size 9M Casual ShoesWOMEN'S SRO MAUI WEDGE HEEL SHOES-SIZE: 8.5MWomen's Brown Leather SAS Loafers Size 9.5 S GREAT ConditionEARTH SIZE 6 B Kalso Technology Black Suede and Patent Leather Exer Clogs SHOESMerrell "Spray Moss" Green Strappy Water Slip-On Shoes, Size 8 Velcro HIKING , COLE HAAN Womens Leather Soled Flat Slip Ons Shoes Size 7 1/2 AASALE! Lucky Brand Lk Elisabeth size 8.5SIMPLY VERA ZEUS BY VERA WANG LADIES OPEN TO WEDGE HEELS IN BLACK SIZE 6.5 M EUCGentle Souls By Kenneth Cole • Essex • Women's 10 M Black Leather slip onsWomen Classics Loafers Canvas Slip-On Flats shoes Lazy Cartoon Cat Size 6-11LifeStride Quizzical Metallic Faux Leather Flats, Women's Size 9.5M, Pewter , Boden Ballet Flats Size 36 5.5 Dark Purple Round Toe Leather Slip On Classic , Hot Chocolate Design Shoes. Floral Design, Women's Size 7,Excellent ConditionLADIES CLARKS BLACK LEATHER SHOES WITH BROAD ELASTICATED STRAP DISCOVERY RITZSC35 Alysonn2 Loafer Ballet Flats, Velvet BlackSugar Womens Goal Casual Slip On Canvas Sneaker , Clarks Springers Shoes Size 6 Medium Brown Leather Woven Loafer S , Asics Gel Venture 5 Womens Running Training Shoes Size 7.5 Black Aqua CoralEasy Spirit Traveltime Slip-ons-Women's size 6 MGreyRockport Mens Moccasin Loafer Suede Indoor Outdoor Slippers Brown 9.5 - 10Womens asics Gel Frantic 7 multi color running shoes sz 10 , EUC Womens 8.5 39 Nike Air Zoom Pegasus 34 LE Sneakers Running Shoes 883269-400Women's Mizuno Wave Lightning RX3 Volley Ball Shoes Sz 9 US , Dolce Vita Women's Dara Ankle Strap Sandal Black Leather/Elastic SandalsNWB ASICS Women's Gel-Harmony TR Cross-Training Shoe Size 7.5 (US) Plum/OrangeSkechers Women's Slicker Fashion SneakerBlack6 M US , Merrell- Zoe Sojourn Ballet Flats, Women's Size 10.5, BlackKeds Women's Lex LTT Fashion Sneaker Gray 7.5 B(M) US , Asics Onitsuka Tiger Women's Cream light tan w/purple trim Size 11 , Reebok Club Memt Shoe Women's Casual Shoe SKU CN1518 Pink Size 6.5
"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."