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.Womens DANSKO Shoes Sz 40 Clogs Oiled Leather Comfort Brown 9.5 10 US , Womens Size 8.5M Clarks Everyday Black Suede Leather Loafers/Heels , Cole Haan Black Suede Tassel Accent Studio Grand Ballet Loafer Flat Shoe 9.5 , Dansko Burgundy Leather Loafer Clog Moc Toe Mule Shoe Women's US 9.5 to 10 , Clarks Privo Women's Size 7 Sneakers Black Leather/ Suede Comfort Walking Shoescrocs Womens Lina Deluxe Ballet Flat- Pick SZ/Color. , Vaneli Van Eli Pink Magenta Leather Snakeskin Moccasins Flats Loafers Size 6.5 M , Thierry Rabotin Taupe Suede Leather Elastic Chris Cross Women's Pump Shoes 36.5 , PLDM Lovell Cash Women's Flat Shoes Black Size 8.5FIDELIO Hallux Helga Magic Stretch Mary Jane Comfort Shoe Women's Size 10 /Vaneli Womens Baffle Flat (B)- Pick SZ/Color. , Robert Zur Womens Shoes Metallic Bronze/Silver Driving Loafers Flats Sz 6M MO39Dr. Martens, Air Cushion Sole^^Size 6<>slip on^black leatherNew Womens Platform NEW Wedge Loafers Sneakers Slip On High Heels Dress ShoeS SZconverse womens new mint green pastel converse 9 , Tretorn Women's EVE3 Sneaker, Blush Perforated, 11 Medium US , Sketchers Women's White Blue Athletic Running Shoes Size 8.5Diadora M Shindano 4 - Blue - Womens , Skechers Women's You-14960 Sneaker, Peach, Size 13.0NIKE WOMENS FLEX 2018 RN RUNNING SHOES -SNEAKERS- AA7408-401- BLUE FORCE /WHITEWhite Mountain Women's Carly Gold Exotic Print Leather , Nike Flex Experience Run 5 Black/White Women's 844729-001 SZ 5NEW Nike MD Runner 2 Women's Classic Shoes Sneakers 749869 - 103 Size 11 , Kappa Shoes Caserta Footwear 3025WK0 C28 Womens Blue Navy Shiny Sneakers CasualWomen's Indigo By Clarks Black Leather Flats 64409 Brand New In Box , Keds Women's Lex LTT Fashion Sneaker Gray 7.5 B(M) USWomen's Asics GT 2000 Black White Electric Blue Running Shoes T2K7N sz 7 , CONVERSE WOMEN'S CTAS MADISON 559892C BLACK/WHITE/BLACK , Under Armour UA Women Micro G Turquoise Shoes size 10 excellent condReebok Womens Easy Tone Fitness Shoes White Pink Size 7.5 Smoothfit. ,
"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."