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.Privo by Clarks Womens Shoes 8 Brown Bronze Mary Janes Walking FlatsSPERRY TOP SIDER WOMENS ANGELFISH NAVY GLITTER SIZE 7M Fishing Boat Shoes Used , REPORT BALLET FLAT VANILA SHOES SIZE 6 (S302)Easy Street Women's Kana Mule, Camo, 6 W US , Women's UNISA Shoes 8.5M Black Leather Loafer Style Slip On Flats , Crocs Slingback Ballet Flats Brown Pink Rubber Slip Ons Womens 10 , Traditional Indian Women Shoes Sandals Slippers Leather Flip-Flops US 6-10Talbots Womens Cassidy Black Suede Loafers Size 11 , MINT COLE HAAN D26350 US 8B Brown Suede Fur Driving Moc Loafers ADr. Scholl's Womens Giorgie Leather Closed Toe Ballet Flats Saddle Size 11.0 l , Chinese Laundry Womens EASY DOES IT Suede Pointed Toe, Black Suede, Size 6.0Aldo Women's Beige Leather Pointed Toe Flats Size 9 , Mens SLIPPERS BEIGE WITH RED STITCHES COLOR HQAcorn Digby Gore Scuff Slippers, Men's - Size 12-13, Black Tweed , Rocket Dog Red Plaid Womens Jagg Altan Cotton Fashion Sneaker Shoes 8.5 M C6317Nice Women's Adidas Climacool Knit Shoes Sz US 7Women's Merrell wood loafers 11 Quality Superior FlatsPuma Women's SUEDE PLATFORM CORE Shoes Whisper White/Puma Black 363559-01 b2016 WMNS Nike Air Force 1 Hi Premium SZ 9.5 Light Bone Gum Bottom 654440-005New CONVERSE WOOLRICH Chuck Taylor Rainbow Plaid High Wool Boots Women's 6 MNew Balance Women's 580 Running Shoe Burgundy Gray Size 8.5Ladies Skechers Trainers Label - Go Walk-Wadidas Athletics 24/7 Tr M Cross TrainerASICS GEL-Ds Trainer 22 - Purple - Womens , Nike Womens Max Air Tennis Shoes Size 8 Pink, Gray, AquaWomen's Under Armour Finisher II MC Lacrosse Cleats - White/Silver/Pink - NIB! , Women's Adidas Mana Bounce 2 W Aramis Pink / Silver / Orange Sz 10.5 B39024Vans ISO 1.5 Moroccan Geo Tan/White Women's Shoes 9.5 - Men's 8 , ASICS Womens T696n DivaBlue/Silver/AquaSplash Running Shoes Size 9 (361693)Asics GT 1000 Womens sz 7 T5A8N WIDE Silver/Pink/Green Running Training Shoes ,
"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."