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.Stuart Weitzman Black Suede Leather Ballet Flats Shoes 9Born BOC Black Leather Clogs with Wedge Heel Slip Ons ~ Sz 6.5 US / 38 EurDonald Pliner Women's Shoes, Sz 6.5 M Brown Fabric Leather Loafers Made in ItalyAlfani Womens Gessey Closed Toe Slide Flats Black Size 5.5Jutti US 6-12 Handmade Women Shoes Maroon Flip-Flops Indian Leather Ballet FlatsSplendid Womens Lydia Dress Round Toe Buckle Flats Shoes BHFO 8518 , LADIES SHOES/FOOTWEAR - Step On Air Diablo black flat shoeNIB WOMEN'S MIA Tristian - Black Nova Suede Tassel Driver SIZE US 10 99$Elegant Footwear Women's Embroidered Rose Floral 90s Round Toe Ballet Flat 8.... , Lucky Brand Womens Emmie Fabric Closed Toe Ballet Flats Ik Chvrn-Mns Size 8.0 , Pinch Toe Dexter Loafers Leather Boat Shoes Womens Size 8.5Ecco Light Black Leather Bicycle Toe Oxford Flats Shoes Womens 41D -10/10.5 D , Volatile Size 7.5 Camo Flats Leather Brushed Hair New Womens Shoes , Birkis Birkenstock Provence Navy Ribbed Birkibuc Mules Clogs 39/L6 M4 NarrowWoman Hand-sewn Leather Loafers Genuine Leather Flat Shoes Flats Women Shoes , Jambu Women’s Blossom US Size 10 Memory Foam worn only onceEasy Street Purpose Slip-On Flats, Black SmoothPROPET WOMEN'S TAUPE/PUTTY PUFFIN LEATHER WALKING SHOES -NWOB- NEW SHOES , Skechers GO WALK 3 INSIGHT Ladies Slip-On Walking Shoes Charcoal [151P] , Women's New Balance 812 Shoes Sneakers Size 8D Wide Beige Leather Walking V7 , Asics Gel-Excite 4 Women's Running Athletic Shoes Size 8 MAdidas Adizero Tempo Sz 8 Pink/White Running Sneakers Shoes For WomenWomen's Converse Chuck Taylor All Star Sequins Ox Low, 136079F Size 6 BlackNike Air Huarache Run Women's Shoes Igloo /Wolf Grey/White 634835-303 SZ 5.5 US , ASICS GEL-Craze Trainer 4 - Blue - WomensMizuno Women's Size 8.5 Wave Rider 19 Running Shoes, Lilac Purple / Silver , Skechers Performance Women's Go Run 400 Running Shoe, Color Options , ECCO Cool Women’s Gore-Tex Surround Cool 2.0 Sneakers Size 8.5 Coral , REEBOK YOUR FLEX TRAINETTE 8.0 LMT AR3236 Stealth Black Cross Training Women 8SKECHERS SHAPE UPS WOMEN'S Fitness Walking Toning Shoes 11806 Size 9 ,
"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."