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.02-1596 Sam Edelman Verona Espadrille Flat - Women's SZ 9.5M , Sanuk Castaway Sidewalk Surfers Sandals WOMEN'S Shoe Sz 5 Black / White StripeCLARKS Womens Size 11 Black Blanche West Flats , Clark's Collection Women's Mary Jane Sport Shoes Blue Size 10MClarks Originals Wallabee Boots Maple Suede Women's Shoes Size 9 MNine West Womens Metallic Leather Loafers Size 9 M , Womens Sz 6.5 37 Black BORN Slip On Loafers Shoes W/Buckle , Trotters Size 8.5 Narrow Light Brown Suede Women’s Slip On Shoes , Women shoes Derby shoes Derby shoes Richelieu Wedge Sole inside New Leather , Klogs Isabella Women's Leather Clogs Display Shoes Model Black 9.5 M , Klogs Melody Womens Clog Shoes Display Model Black 9.5 MKEEN MJ Casual Shoes, Brown, Leather, Women's US Size 8.5Women Rivet Pointy Toe Cuban Heel Big Buckle Studded Shoe Pumps Leather Loafers**Dr. Scholl's Madison Slip On - Women's Size 6M - Black , Dansko Portia Womens 41 10.5-11 Black Leather Mary Jane Slip-On Buckle Shoes z8MUK LUKS Men's Double Gore Printed Berber Suede Slip On , New balance Memory foam Womens 8.5Womens Size 9.5 ASICS GEL CONTEND 4 T765N INDIGO BLUE Running SneakersWomen's Nike Leather Golf Shoes Sz 8.5NIKE 'Air Max 90' Purple Rave Pink Running Shoes Sneakers Women's Sz. 10.5 , NIKE DUAL FUSION RUN 525752-003 WOMENS , NWOB Adidas VIGOR BOUNCE Trail Runner Shoes Grey Glo Orange Women's Size 7 , New Balance W52ORN2 Women Shoes Comfort Running Walking Navy 9 M Wore OnceAdidas Springblade Drive 2 Grey Athletic Running Shoes D69711 Women's Size 9.5Propet RidgeWalker Low - Women's Orthopedic Hiking Shoe - All Colors - All SizesNEW Ryka Women's Faze Athletic Shoes Slip-on Sneaker Comfort Size US 9.5 M $75BROOKS DYAD 8 WOMENS ATHLETIC RUNNING SHOES SIZE 7.5 WHITE NAVY TEAL , Ryka Hypnotic Running Training Fitness Athletic Shoes Sneakers Green Womens 10Abeo Aero Sytem Cross Training Running Tennis Shoes Women's Size US 9 VibramNEW BALANCE SIZE 6.5M WOMENS TRAINING RUNNING SHOES LIGHTWEIGHT GRAY ORANGE ,
"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."