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.RELIFE Womens Ladies EEE Wide Fit Flat Shoes Sandals PumpsWomen's Think! Orange slip on sneaker loafer Fall Autumn suede button 39 8.5/9 , Women’s White And Blue Stripe White Mountain Flats Size 9.5 WPrivo CLARKS Women's Slip-On Straps Flats comfort WALKING casual Shoe 8.5MMt Emey 9108 Womens Supra-depth Shoes Size 7 (AA) Orthopedic Diabetic Support , New Women Wild Diva Pippa257 Faux Suede Pointy Toe Rose Patch Motif Slip On Mule , New Crocs Women's Gretel Fur Lined Clog, Blue, Brown, Black, Pink, Size 4, 5, 6Cole Haan 9.5B Women Flats Shoes Tan & Cream LeatherKlogs Myra Women's Clogs Display Model Shoes Butterfly 7 MNEW GINO VENTORI BEHOLDER WOMENS COMFORTABLE LEATHER LASER CUT FLATSKLOGS VALLEY WOMEN'S LEATHER CLOGS DISPLAY MODEL RED CRINKLE PATENT 7 M "AS IS" , Everlast? Sport Women's Andi Pink Athletic Shoe - Size:7,M new , New Kenneth Cole White Jovie Leather Sneakers Shoes Sizes 7-10Womens rhinestone square toe slip on flat heels fashion casual shoes hot a592Converse Chuck Taylor II All Star W/Lunarlon UNISEX SHOE (Mens 9 Wo's 11)Skechers Womens Relaxed Fit Sure Track Trickel Black Leather Work Shoes Size 7.5NEW! WOMENS SKECHERS SYNERGY 2.0 - MIRROR IMAGE 12386 GREY/MINT 119S pmNEW G.H. BASS & CO Women's Shoes NAVIGATE Casual Nautical Low Top Sneakers sz 7 , Women's WOMENS SHOES BY LANE BRYANT Customers First FlatsPaws Print Basset Hound (Black/White) Running Shoes For Women-Express DeliveryNikeLab Air Zoom Fearless Flyknit Running Shoes Trainers 878558 400 US 7Nike Womens Special Field Air Force 1 One High Black SF AF1 AA3965-001 Sz 11.5Women Sneakers Reebok CM9003 Jet Dashride 6.0 Running shoes black grey yellow , Ladies Superga 2750 Ukfglu Tennis Shoe Casual Classic Plimsoll Trainer All SizesKeen Womens Koven Waterproof Hiking Trail Athletic Raven Blue Shoes Size 11317581-601 Nike Womens Blazer Low Classic Carnation Black KhakiH by Halston Snake Embossed Leather Slip-On Sneaker Shoe Susan Cream Women's 5.5 , Propet RidgeWalker Low - Women's Orthopedic Hiking Shoe - All Colors - All SizesNew Saucony Womens Vendetta Pink/White Running Shoes Size 11 , BOBS Women's Skechers Alpine S'Mores Ankle Booties 34134/CHOC Chocolat Brand New ,
"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."