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.SELF ESTEEM Women's Black Ankle Strap Pointy Ballerina Skimmers Flats Size 7.5 M , Born mary jane leather flats womens size 8 / 39 W-6856 brown slip on slides , Hawkwell Women Mule Moccasins Buckle Penny Slip-On Backless Loafer Shoes , DONLAD J PLINER Lisa 'Fara' Studded Leather Ballet Flat (5.5 US) Reg $189Luxury Rebel Womens Sari Black Wrap Ballet Flats Shoes 6 Medium (B,M) BHFO 3598Hush Puppies Womens Dress Pump- Brown 7 1/2US , DC GRAFFIK WOMEN'S SKATEBOARD SHOE, SIZE 7.5, SLIP ON TEXTILE FLAT W RUBBER SOLE , Corkys Sidewalk - Bronze - Womens 9Skechers Moments Loafers, Women's Size 6, Blue , Fashion Sneakers Woman Flats Loafers Round Toe Comfortable ballet Flats ladiesSkechers BOBS from Women's Bobs Plush-Peace and Love Taupe 10 B(M) US , Ecco Womens Navy Blue Clog Mules Size 40/9-9.5 US , LFL by Lust for Life Women's Tinker Ballet Flat, Blue, 7 M USJack Rogers 1117FF0002 Womens Bennett Etched Fashion Sneaker- Choose SZ/Color. , Calvin Klein Jeans GABY slip on SHINY NYLON/SUEDE BLACk sale re9184ALL BLACK, SUMMER BALLET FLAT, WOMENS, RED, US 6.5 M, EURO 37, NEW/ DISPLAYDEXTER Womens 5 LEATHER TASSEL KILTIE LOAFERS OXFORDS MOCCASIN Shoes USA MADESkechers Comfort Air - Just A Lil Knit Navy Womens Sneakers Size 7.5MSuperga New Linembrw Blue Womens Shoes Size 10 M Flats MSRP $159 , New! Women Skechers 14018 Go Flex Walk Muse Slip On SIZE 6.5 Blk/Gry O7002-2494 ALTRA Women's Torin 2.5 Gray/Raspberry Running SIZE 6Adidas Element Voyager 2 Womens Textile Green Running Trainers Shoes B44339 U87Skechers for Work Women's BISCO Slip Resistant Wor - Choose SZ/colorWomens Nike Lunarepic Flyknit Running Shoes Size 7 - 10 Black White 818677 007 , Charolais Cattle Cow Christmas Running Shoes For Women- Free Shipping , Spira Dd Pretty Pink Special Edition Women's ShoesAsics Gel-Kayano 24 Athletic Shoes - Women's Size 8.5, Slate Blue/Coral , Oboz Womens Luna Low Athletic Support Leather Hiking Trail Athletic Shoes 8.5Adidas Originals SL72 Womens Sports Shoes Suede Sneakers Casual Leather US 5.5 , New KEEN Womens Lower East GothicOlive Fashion Shoes Size 5.5 ,
"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."