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.Calvin Klein Size 7M Ballet Flats Elaine Black Patent Laser Cut , Minnetonka Women's Kilty Suede Moccasin - US SIZE 5.5Bellini "Vegas" Brown Alligator Look Leather Slip Ons Size 7M 1 3/8" HeelsWomen Hand Painted Personalized Canvas Slip On Loafers Flats Skateboard Shoes , MERRELL ENCORE Black Mesh Clogs Womens Size 6.5 , earth womens sz6.5B shoe slip on brown leatherside zip side elastic insertDANSKO Women OLIVIA SLIP-ON Shiny Black Leather Low Loafer Shoes 36 6 M , MESSECA NEW YORK, BRAZIL LADIES SIZE US 6, BLUE FUR LEOPARD PRINT FLATS , Steven By Steve Madden Keats Casual Slip On Shoes - Women's Size 10 M - Black , Clarks Black Suede Mary Jane Tamitha Aster Comfort Shoe NewKeds Chillax Slip-On Oxford Sneaker Women Black Size 5MFashion Women's Soft Cow Leather Pointed Toe Mules Oxfords Slides Slippers Pumps , Under Armour Micro G Assert IV Womens Running Training Shoes Size 7.5 Gray Pink , Gently Used Ladies Authentic Cleat Athletic Shoes, Size 3.5 GOOD COND , Ryka “Aurora” Tan Water Resistant High Top Sneaker Boot Women’s Size 12M , ALTRA Women's Olympus Gaiter Trap Zero Drop Shoes Pink Orange Size 7.5 , New Balance WSTROCW1 Women Size 6.5 Silver White Running Shoes F2-226 , Saucony Womens - Black Running Shoes Size 8 (344943)Women's Under armour women sneakers 7 Bargain Price Athletic ShoesWomen's Kids Steve Madden Sneakers Low-priced Athletic ShoesTommy Hilfiger Women's Fressia Sneaker - Choose SZ/Color , Nike 683818 Womens Air Huarache Run Premium Low Top Running Sneakers Shoes , Women New Balance W790RO6 Running Medium Ozone Blue Lime 100% Authentic B. New , Brooks Womens Neuro 2 Blue Running Shoes Size 8 (25298)Brooks GTS Seventenn Sneaker - Women's Size 11M Black/Purple , New Balance 580 WRT580RK Women's Black (Size 7 - 9.5) Capsule CollectionWomen's Puma Ignite v2 18861207 Black-White-Pink Glow Brand New in Box , Fila J319R Pink Black Women Running Shoes Sneakers 5-J319-R240New Balance Womens - Blue Running Shoes Size 12 (415447)New Balance W575LI2 Women's Mesh Lightweight Breathable Cush+ Low Top 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."