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.WHITE MOUNTAIN HOME PORT Gold Platinum Leather Dock Siders Boat Casual Shoes 6.5Women's U.S. Polo Assn. Priscila Gray/ White Slip-On Casual Shoes Size 5.5 M , wcozy02m fluffy slides sandal TAUPE 6 (size 6.5 7 7.5 8 8.5 9 10 upon request) , Pandamerica Mary Jane black cotton fabric upper classic peggy maryjane . , SAS Womens 7.5 WWW Extra Wide Shoes Comfort Casual Black Adjustable Walking , CLARKS Womens Sillian Jetay Closed Toe Loafers, Black, Size 8.0 hwVX , LL Bean Boat Loafer Deck Shoe Women size 7.5 NavyVIONIC Womens Grey Snake Print Patent Ballet Flats Slip On Elastic Shoes Sz 7.5Simply Vera Wang Flats Shoes Mumbai Metallic studs ties sz 7 NEWCalico Women's Blue Fabric Slingback Flats Size 7 W , Amalfi By Rangoni Shoes Size 6M Womens Black Slip On FlatsKeds Mens Champion Heather Gray Felt Sneaker 7.5M , Obession Rules REA Black REA Women's SZ 8.5Womens Gray & White ADIDAS Athletic Sneakers Shoes Sz 6.5La Redoute Collections Womens Ballet Pumps With Embroidered MotifsNew Balance Womens Tennis Volleyball White Athletic Court White Shoes Size 9Puma Popcat Red White Barbados Men Lifestyle Sandal Slide Slippers 360265-13 , New Balance XLT 540v2 Athletic Running Sneaker Shoe Blue Silver White 6 M Women , Asics GEL-Cumulus 17 Women's Aqua Mint/Yellow/Navy Running Shoe 10MPuma Size 6 Taz Prima Women's Running Shoes Aurba Blue and Silver , Ryka Divya Training Sneaker - Women's Size 9M - Black , Puma Womens Suede Classic FT Beige Fashion Sneakers 6 Medium (B,M) BHFO 2016New Skechers USA Gray Metallic Slip On Casual Summer Active Wear Shoes 7 , Nike Dunk RARE Wms/Girls SZ 8.5 Blk/Turq/red/ 370685-991 NIKEID Peyton BB shoes , Adidas Tucana Packaway Women Trainers in Blue D66475 [/3] , Lucky Brand Bayleah High-Top Fashion Sneakers 682, Brindle, 5.5 US / 35.5 EU , Reebok Yourflex Trainette 8.0 LMT Women's Training Shoes Sz.9 US Blue NWOBPropet Vista Strap - Women's A5500 Diabetic Comfort Shoes - All Colors - All Si , NEW BALANCE W690LZ4 BLUE/PINK RUNNING SHOE WOMENS SIZE 6.5 B(M) USEasy Spirit Size 8 Brown Leather Slip On New Womens 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."