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.SE BOUTIQUE Magenta Snake leather ballet 6 USA 36 EUWomens Ladies Diamante Flat Jelly Sandals Summer Flip Flops Open Toe Post Beach , Aldo fashion sneakers silver metallic with white sole size 8 Women.AGL Flats Shoes Women Size 37.5 US 6.5 Black LeatherSC35 Audreyy Wrap Bow Ballet Flats, Light Gold , Lanvin Taupe Suede Round Toe Stretch Fit Ballet Flat Shoes Size 8Women Munro Shock Absorbing Heel black slip on shoes w/ Dansko inserts, 9 MAnne Klein Zilya Elastic Espadrille Flats 438, Metallic Tan/Tan, 9 US , CLARKS ARTISAN Women's 73267 Black Woven Leather Clogs Sz 11 M Slides Mules #C23naturalizer Villa Backless Penny Loafers 596, Saddle Tan, 8 US / 38 EU , Zara Womens Shoes Sz 6.5 Euro 37 Neon Yellow Stilleto High Heel NwtAerosoles Drive Through Slip-On Loafers, Black Snake, 7.5 USLifeStride Womens dee Suede Closed Toe, Tan, Size 9.0 upa3Teva Shoes Women's Size 9 Blue Gray Beach Sport Slip OnDakota Quad Lite Aluminum Toe Composite Plate Women's Black Athletic Shoes 9WEasy Street Women's Kacey Flat, Black Flannel/Snake, 7.5 2W USTUK BLUE BLACK PLAID CLOTH SUEDE LEATHER CREEPERS A8055 UNISEX 6 M / 8 W NOS , New BIRKENSTOCK ARIZONA (051703) Brown Women Men Slippers Sandals All SzNEW KEEN MADERAS OXFORD SHOES WOMENS 6 PURPLE STYLE: 1008850 FREE SHIP , Nike Sport Performance T.A.C. Golf Shoes Cleats Black 314914-016 Women's Sz 8B , Skechers Go Walk Black Glow Lightweight Slip on Shoe NEWMERRELL Satelite Mock Pale Pink Leather Stretch Trail Hike Shoes Women's SZ 7.5Nike Dual Fusion Run2 Grey/Blue/Pink 599564-002 Women's Running - Size 8Vasque Womens Talus Trek Low UltraDry Leather Athletic Support Hiking Shoes 9Women's Sperry Windsor Patent Loafer Aesthetic Appearance FlatsWomens ADIDAS PUREBOOST Q4 Black Textile Running Trainers M21408New Under Armour Women's Dash 2 Running Shoes - Size 7.5 - Black / Glacier GraySiberian Husky Canvas Shoes, High Top, Women Men, Pet Dog Lover Gift Galaxy Wolf$110 Women's Size 7 Brooks Ravenna 8 Running Shoes , Skechers Women's GOwalk 4 Achiever Slip On Walking Shoe ,
"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."