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.RF Room Of Fashion Easy05 Rose Low Block Heel Mule Loafer Slides Flats WHITEAdorable Cathy Din Women or Girls 8.5 Shoes Flats - Black with Animal PrintGeox Navy Blue Suede Driver Loafers Size 40 10PRIVO CLARKS Ricegrass Purple Suede Waterproof Loafers Shoes Sz 6.5 M , AIRWALK Size 8 M Striped Pink Orange Green Canvas Sporty Fashion Sneakers , NEW Sperry Top Sider Women US SIZE 6 Black LoaferRocket Dog Women's Shoes Size Us 6/39 Black Leather Tassel Flats Slip On OxfordsClarks Womens Ballet Flats Black Leather Size 11 , NEW Womens Black 8 Simply Vera Vera Wang Sperry Size 8 Ankle Boots Shoes $89.99Karen Scott Chandii Women Round Toe Synthetic Ballet Flats Black Size 7.5 , 9 Lavender Orchid Beaded Flats Handmade Belly Dance Indian Khussa Sari Shoes , NEW!! Catherine Malandrino Forrow Red Velvet Slides Mules Size 8.5M US 38.5M EU , MUNRO Womens Size 9.5 Skipper Stone Nubuck Leather Perforated Slip On 9.5 , Munro Berkley Women's Dark Brown Leather Wedge Casual Loafer Shoes US Size 11 W , Christian Siriano Gigi womens black white striped pointy ballet flats 6.5W wide , Liendo By Seychelles Womens Ronda Ruffle Wedge Shoes Navy Size 6 NewNew AERIN Imogen Calf Hair Pointed Toe Flats Size 6.5 MSRP $295 , Reef Rover Low TX Sneaker - Women's Size 9 BlueTeva Shoes Women's Size 9 Blue Gray Beach Sport Slip On , Alfani Womens ALEEA Closed Toe Ballet Flats Grey Size 5.5 , Maypol Espadrille Shoes Sz 45 US 14 BlushSoft Suede Leather Flats AnthropologieNew Amalfi OSTE Navy Blue Flats Loafers sz. 7 M Nena NappaFashion Women's Straps Sports Running Sneakers Embroidery Flower ShoesGRASSHOPPERS Womens Canvas Slides Slip On Shoes Red Sz 7.5M - Very Nice!Merrell 8.5 womens mens Hiking Shoes leather waterproofBrooks Adrenaline GTS 14 Running Shoes Womens Size 7 Hot Pink Black Silver Nice , MERRELL Women's J21242 Azura Jaunt (Otter) Brown Suede Leather Hiking Shoes 10 , NIB PUMA 2 pairs REBEL MID VR WOMEN'S TRAINING SHOES Training Running Gym ShoesNike Free Transform Flyknit OC Unlimited Olympics Wmn's 843990-999 SZ 5.5 , NEW!! Ladies SZ. 8.5 Adidas P Absolado LZ TRX FG W Blue White Pink Soccer Kleats
"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."