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.Anne Klein Aricia Bow Toe Ballet Flats 573, Black, 9 US , Crocs Springi Pink Slingback For Women Sz 10M - NWOB $39.99 , Anne Klein Black Alligator Flats Shoes Iflex Size 7.5 Ladies Womens New NibLadies Rockport Adiprene Plum Suede Leather Shoes SK71917Jutti Women Shoes Punjabi Flip-flops Leather Indian Handmade Ballerinas US 12Johnston & Murphy Domani Size 7 M Dress Shoes Italian Made Loafer Moccasin Toe , Womens Naturalizer Mules/Clogs 9M Black Leather Slip On Loafers Casual SlippersMerrell Women's Tan Improv Moc Tumbleweed Hiking Walking Size 6.5 , Antonio Melani Size 7.5 Gold Leather Flats New Womens ShoesEasy Spirit Karne suede leather oxfords brown 8.5 Md NEWNew Women's Skechers Flex Appeal 2.0 Done Deal Casual Walking Shoes 12769 pc 18T , NIKE AIR Zoom Structure 20 Women’s Athletic Running Shoes Size 11 , NIKE womens synthetic lite weight in purple,lime,lavender 7M in excellent cond.REEBOK WOMEN'S WHITE FASHION SNEAKERS SZ 7.5 in VERY GOOD CONDITION , K-Swiss Women's Hoke CMF Sneaker - Choose SZ/Color(511882-111) WOMEN'S NIKE ROSHE ONE WHITE/WHITE , Puma Basket Heart Suede Jr Halogen Blue Lilac 3 4 5 6 SportsLocker 365009-06New Balance Women's 580 Classic Sneakers Shoes WRT580WE Suede Medium (B, M) , NIKE Dual Fusion Run Black/Fireberry Sneakers Sz 9.5 , Valentine's Day Special-Pekingese Dog Print Running Shoes For Women-Free ShippinAsics Womens Gel Lyte V Vanilla Cream White Sprinkles H7Z9L-0202 Msrp $120 KCNike Tanjun Gray White For Women's Youth Size New In Box 818384 003 , NEW! ASICS Women's GEL-Cumulus 19 Running Shoes Black/Pink #T7B8N 103A pzNIKE Womens Hyperize Black/White/Silver Shoes Size 8.5 , Nike Women's Air Force 1 07 Low Size 8 , PUMA Tsugi Jun Sneakers - Women's Size 11 - CreamWomen's Salomon X-Celerate 2 Sports Trail Running Trainers Shoes , Adidas CrazyTrain Elite Women's Training Shoes Sz.6.5 US Black NWOB , Skechers Women's Go Step Lite-GLITZ 14724 Black Goga Max Foam Brand New , Converse CT Shoreline Slip 537080F Navy Canvas Casual Women's Shoes Size 8 M ,
"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."