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.SAS Jewel Brown Leather Comfort Flats O-Ring Loafers Slip On Shoes Women's 8 M , Yellow Multi Floral Print Ankle Strappy Point Toe Fashion Women Ballet Flats , Lucky Brand Women's Clogs Shoes Brown SZ 8M Suede Leather PACE LOVE Boho Wedge , CROCS *LINA* CHEETAH PRINT BALLET FLAT - LADIES 8 - ONLY WORN A COUPLE TIMES! , Qupid Women's Espadrille Ballerina Ballet Flat , Ladies Womens Flat Low Wedge Platform Heel Diamante Holiday Summer Sandals Shoes , Croft and Barrow womens shoes loafers leopard pattern size 7 NEWWomen's SAFE T STEP Work Shoes 9.5M Black Silver Comfort Clogs Slip-resistant , **VIONIC Valeri Slip On - Women's Size 9 BlackWomen's Tesori Beige/Black Espadrilles Size 8.5 MWomens Cole Haan 8 B Maria Sharapova Beige Leather Dress Flats A077Womens Enzo Angiolini Liberty Beetroot Color Shoes IWOMEN'S SHOES SNEAKERS CROCS CAP TOE FLAT [12300 BRONZE/GOLD]Asics GLS Women's Running Athletic Shoes Size Gray T28AQ US 7 M , Steven By Steve Madden Womens Glimmer Taupe Fashion Sneakers 8 Medium (B,M) 3920Nike Zoom Pegasus 26 + Running Shoes, Lime/Blue/Silver, Womens 7.5Eric Michael Candace Womens Suede Espadrilles Slip On Elastic Ankle Shoes , Cobb Hill Womens galway Leather Closed Toe, Black, Size 11.0 vaPONew Retro Womens Horse Hair Leather Pointed Toe High Platform Pumps Casual Shoes , J-41 Adventure On Slip On Walking Water Hiking Shoes Orange Tan Womens Sz 8 , Capezio Womens eos Low Top Pull On Walking Shoes , fashion Womens ladies Glitter Beads Slip On rivet Casual point toe flat Shoes , BROOKS PureCadence 4 Running Fitness Crossfit Marathon Jog Shoes Women Size 8Merrell Tuskora Aluminum/Aqua - Women's Hiking Shoes/Boots - Size 8.5 / , Brooks Womens Chariot AquaSky/BlueRibbon Running Shoe 7.5 Women USSTEVEN Steve Madden Arden Slip On Fashion Sneakers, GreySkechers Sport Women's Galaxies Fashion Sneaker - Choose SZ/ColorPOLO RALPH LAUREN FASHION SHOES RED YELLOW BLACK - 11D ESPANA 67VANS Era Hi (Pig Suede Nylon) Black/Blanc Suede Skate Shoes WOMEN'S 8 , WOMENS NIKE EXTREME VOLLEY TRAINING SHOES size 14 VERY NICE!
"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."