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.Nurture shoes womens size 8.5M brown leather clogs slip on comfortSporto Jasmine2 Faux Fur Lined Slippers 75188, Red, 7 US Used , G.H. Bass & Co. Bass-Becca Women's Brown/Blue Slip On Loafers 7.5M , American Sweetheart women BROWN felt like sneakers SZ 9 M NEW , Clarks Blue Suede CONCERT JAZZ Ballet Flat--Size 7.5M , VIONIC Telma Periwinkle Blue Orthaheel Orthotic Sling-back Clog Women 8 M (39)LANDS END Purple Canvas Mary Janes WOMENS BOAT LOAFERS MULES SHOES SIZE 5 ❤️ , Cape Robbin PIXIE-2 Nude Blush Almond Toe Slip-On Flat Mule Rhinestones , HUSH PUPPIES 100% Relax Womens 11M Brown Leather Slip On Casual Walking Shoe , Tory Burch Reva white Quilted Flats sz 8 gold medallionHush Puppies Cille Gwen Sneaker - Women's Size 9.5 M, Black Crackle , Marc Fisher Womens Apala Pointed Toe Ballet Flats, Blue, Size 6.5 , Mizuno Baseball 9 Spike Black Leather Mens Size 12 , Womens Asics Gel Blur 33 TR Purple Running Athletic Shoes Sz. 8Youth Grey Converse One Star Lowtops, Size 4Vintage Dr. Martens Black Monk Strap Oxfords**Skechers Classic Fit Sneaker's Women's Grey - Size 9 Memory Foam , Skechers FLEX APPEAL-OBVIOUS CHOICE Ladies Sports Gym Trainers Charcoal/Aqua -6 , NEW EVERLAST BREEZE WOMENS CASUAL SLIP ON SHOESWomens Adidas Grey Shoes Athletic Sneakers Suede 7 , Skechers Shoes Slip On Memory Foam Light Weight Brown Women's Size 7.5Women's Naturalizer Women's Junction Fashion Sneaker Moderate Price Athletic Shoes , Women's Colorful Casual Flats Size 8 Superior Quality Flats , Nike Women's LunarMTRL+ Running Shoes 522346 606 PINK Flash SZ: 7 (24CM) , NEW NIKE WOMEN'S AF1 FLYKNIT LOW SHOES BLACK BLUT tint game royal 820256 004 , NIB Nike Women's FLEX 2016 RN Shoes (830751 800, Bright Mango/White, Size: 6.5)NEW BALANCE W580AB4 WOMEN'S BLACK WALKING RUNNING SHOES sz 5.5 (D) WIDE , LA MAISON DE THE ESPADRILLE Wedge 939 bronze , MICKEY Unlimited ~ Women's Mickey Mouse Canvas Tennis Shoes ~ Size 8USPF Flyers Sneakers Women's Size 7.5 Plaid Green Pink 38.5 Eur 5.5 UK 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."