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.SAS COMFORT LOAFERS BLACK SHOES SIZE 7.5 NSoft Style Women's Veda Monk Strap Flat, Dark Brown Lizard, 6.5 M US , Bakers Dark Red Casual Hiking Shoes - Size 9 - Excellent Condition! , LADIES SPOT ON FLAT SLIP ON SHOE IN BLACK & BURGUNDY STYLE - F8827BOC by Born Women’s Peggy Red Clogs Slip On Shoes CBTF13 Size 8 M 39 GUCSperry Top-Sider sz 6 NIB $90 Audrey Brown Python Boat Shoes Beautiful!! , COLE HAAN Women's Size 7.5 ZeroGrand OS Slip-On Shoes Sneaker Grey Black D44030 , Circus by Sam Edelman Womens Tanner Fabric Closed Toe Cinnamon Size 7.0 , Women's Shoes Franco Sarto ATRIUM Gladiator Flat Sandal Zipper Dijon02-915 Ryka Influence Women's Cross-Trainers, Oxford, SIZE 8MMojari Indian Handmade Leather Women Shoes Casual Ballet Flats US 5.5-7.5 , Ahnu Jackie Pro Black Leather 6 , Skechers Go Step Challenge Womens Slip On Walking Shoes Size 7 Blue GrayNew Balance 811 Walking Shoes Sneakers WW811BE Beige Leather 9 2AEasy Spirit Running Shoes Black Synthetic Women7Medium (B, M) , Women’s Ryka Indigo Athletic Running Sneakers Shoes Re-Zorb Lite Size 11 MBalance FuelCore Nergize V1 Womens Size 7.5 Light Grey Training Shoes F4-551 , Skechers Bikers Point Blank 21363 Womens Size 6.5 , Under Armour Womens Charged Pivot Low Neutral Sneaker Shoe Steel Grey Size 11 MWomen's WR996EG New Balance Consumers First Athletic Shoes , Women's NEW Naturalizer Shoes Size 10 Good Design Flats , Vibram FiveFingers Treksport W4485 Womens size 37 Barefoot Running Shoes , Skechers BOBS Women's Bobs Squad-Awsome Sauce Sneaker , NEW Nike Air Zoom Streak5 Cross Training Running 641318 108Puma Fierce EvoKnit Womens Slip On Navy Pink Woven Trainers 189456 02 D37 , Oboz Womens Sawtooth Athletic Support Hiking Trail Athletic Shoes Size 6Skechers Women's Hi-Lites SPARKLE STEPPERS 984/BLK Black Brand New In Box , Altra Intuition 3.5 Women's Hemlock/Pewter Sneakers 7MSkechers Shape Ups Resalyte Womens Size 9.5 Black White 12471BROOKS Glycerin 13 3D Fit Print Metallic Women’s Running Athletic Shoes Size 8 ,
"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."