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.Soft Style by Hush Puppies Gold Women's Ballet Flat 9 MClarks Artisan Collection Brown Leather Mules Clogs Shoes Womens Size 9M 35726 , Pare soleil CARS * NEUF * Envoi express ou remise en main propreMEPHISTO Size 9 Brown Cola Patent Alligator Print Mules Flats Shoes w/ Cool AirStuart Weitzman Sz 6.5 CIA Beige Croc Made in Spain Slip On Mule Loafer BuckleJSPORT BY Jambu WATER-READY SHOES WOMENS SIZE 7 MMerrell Women's Plie Taupe Leather Maryjane Slip On Flats size 6.5Sperry Top Sider Boat Shoes Womens 9.5 Brown Suede Leather Mesh STS 92468 60304 , CLOGS BY KLOGS VIVIAN WOMEN'S DISPLAY MODEL SHOES CHOCOLATE DISTRESSED 7.5 M , Tory Burch Womens 9 M Black Suede Moccasin Loafers. “Wonderful Condition!”) , Womens Black Vans Flat Bottom Shoes Size 7$77.99 Hello Kitty Womens Sofia (gold) MW1D01-GLD , Womens Athletic Style Slip On Sport Shoes Fall Casual Breathable Running LoafersMizuno Wave Inspire 10 Blue/Yellow J1GD144410 Women's Runing/Training Shoes SZ8Steven By Steve Madden Catie Slip-On Black Size: 8.5MBT Lami Grey Leather Purple Walking Rocker Toning Mary Jane Sneaker Sz 9.5 10Keds Womens DOUBLE DECKER Canvas Low Top Pull On Fashion, quilt gray, Size 8.0 z , NWOB KEDS CHAMPION METALLIC LINEN WF57956 WOMEN'S SHOES SIZE US 11 MEcco Womens Shoes Size 38 Black Leather Spikeless Golf Street Shoe Pink Sneaker , New Zara Basic Women Leather Like Gold Metallic Sneakers Elastic 8New Olukai 20271 2020 Pehuea Tapa / Tapa Women's Slip On Shoes 9 USNike Women's Flex Supreme TR 5 Training Shoe, Black/White-Pure Platinum, 8.5 , Rachel Zoe Women's Burke Clouds Sneaker, Gold, 10 M USWomens Nike PRE Montreal RCR VintageCreative Recreation WCR4LO38 Grape Salmon Cesario shoes , Nike Air Max 2014 Women’s Running Shoes Dark Volt 621078-200 Sz 10 EUC PinkConverse Women’s Size 7 Black White Pink CT All Star Lo Top Sneaker Shoes F2-360Onemix Air Cushion Running Shoes Walking Sneakers Sport Trainers Women's US 6.5Women's Skechers Burst-Positive Image White 12793/WHT Air-Cooled Memory FoamNew Balance Womens W590V5 Running Shoe- Pick SZ/Color. ,
"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."