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.COLUMBIA SAMPLE WOMEN'S SIRENA LEATHER UPPER MARY JANE WATER BOAT SHOES US 7 , Annie Plaza Womens Grey Suede Flat 8.5M , Womens Sperry Top Sider Maroon Suede Shoes Size 7.5M EUC , Clarks Everyday Women Shoes Black Flats Leather Croc Embossed Sz 8.5 83060Liliana Women Carnival-1 Multi Colorful 3D Flower Decor Open Toe Flat Mule Slide , Ladies Vagabond Tia Festival Open Toe Strappy Flat Casual Work Sandals All SizesSAS Tripad Comfort Womens Shoes SIMPLIFY Brown Leather Loafers Size7M 7 Mnaturalizer Stella Pointed Ballet Flats, LilacVery Volatile Size 8.5 M Skye Black Leather Brushed Hair Flats New Womens Shoes , Nike Air Max Trainer One SL Women's Running Shoe White Blue Volt 407867-111 8.5Billabong Women's Addy Fashion Sneaker Seagrass Size 7.0 sGcjSkechers Womens Unity Elusive Comfort Memory Foam Slip On Shoes , Cole Haan Womens Waterproof Mule Shoes Sz 8.5B Black Suede Slip On Zip Up Euc , Nike Womens Size 8.5 XT Quick Fit Dly Wire Training Shoes 415257-101 , PUMA TUNA Cat B2 Jr sz 6.5Y = 8 Women Medium NEW 38.5eu WHITE / Black RunningQupid Womens Moira-07 Khaki Fashion Sneaker Size 6.5 (33850)Tretorn Womens Wtmatchhi3 NewDarkSky/NewDarkSky Fashion Shoes Size 8.5 (340031)Onitsuka Tiger Serrano Women's White/White Sneaker 7MNWT Superga 2750 White Mesh Sneaker Tennis Fashion Shoes Size 8 , Asics Womens Gel Flux 3 Sneakers Size 6.5 Running ShoesKeuka SureGrip Women's Carrie Black Hi-Top Slip Resistant ShoesWomen's Converse women's shoes size 8 Unusual Athletic Shoes , Women's Dyeables Women's Becky Fast Shipping FlatsINDIVI Shoes 974285 Silver 23.5ｃｍ , Roxy Women's Bayshore Slip on Shoe Sneaker - Choose SZ/Color , ASICS Womens GT-1000 6 Running-Shoes- Pick SZ/Color. , Womens New Balance WX813BK2 Black Training Shoes Sz 10B NWOB $90Mizuno Wave Rider 19 Running Shoe Grey/Teal Women's US 10 Eur 42 (L3,20)Vans Off the Wall Womens Surf Shoes Palisades Vulc Distressed Teal Womens 5 , BROOKS GLYCERIN 14 Aruba Blue Anthracite Purple Love running shoe . women’s 11 ,
"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."