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.Womens Franco Sarto Axel Black Patent Leather Open Toe Heels Shoes 6 1/2 M VGCAmerican Apparel Lattice Jelly Peep Toe Ballet Flat Sandal Clear Navy Blue 6 , Women's Sperry Topsiders floral blue white striped 7 loafers shoes , Women's Leather Single Shoes Casual Driving Moccasin Flats Loafers Soft Slip On , Crocs Faux Fur Lined Slip on Womens Shoes Ballet Flats Dark Gray Grey Size 6 WWomen's Merrell Emma Black Slip On Leather Shoes 5.5 M $119 , TROTTERS LIZ DRESSY LOAFER BROWN WOVEN LEATHER WOMEN'S 7.5NWomen's Talbots Vintage Brown Faux Alligator Loafers 8.5 M , Steve Madden Gernade Casual Slip On Shoes - Women's Size 9, GoldMunro American Berkley Women's Black Loafer 5.5MSKETCHER SLIDE ONS Shoe SIZE 6.5, MEMORY FOAMUS Shoe Size Women Wide Width Comfortable Slip On Casual Round Toe Ballet FlatsINC International Concepts Womens Crescent Fabric Pointed Toe Slide Flats SZ 8.5Women's KEDS White Perforated Leather Slip On Sneakers Size 9.5New Balance 750 v1Womens SZ 6 Running NB Athletic Shoes BLACK PINK , Eileen Fisher Womens Sneakers Size 6.5 Brown Gray Round Toe Hi Top SuedePuma Brown Purple Pink Running Training Sport Sneaker Shoe Women's Size 8 , Womens Merrell Siren Sport Vibram Trail Hiking Shoes - Elephant Gray Pink - Sz 7 , Women's Jungla Ladies Leather Lined Shoes Attractive And Durable FlatsPUMA Women's Fenty X High Top Trainer Sneakers Whisper White/Whisper WhiteNike Free Rn 2017 Le Women Shoes Size 9 New!ASICS Womens - Silver Walking Shoes Size 11 (327573) , Nike Women's Zoom Winflo 4 Athletic Running Shoes Grey/Volt/Platinum Size 6.5MAdidas Womens Liquid Ride Running Shoes Black/Baby Blue/Pink G99575 #BRWomen Reebok Z Quick Trainer M44155 Pink Blue Navy 100% Authentic Brand NewNike Free RN 2018 Sneaker - Women's Size 6 BlackConverse All Star Women's CT OX Black/Silver/White Sneakers-Sz 8/9 NWOB 159716FSkechers Taupe Glider Stunner Flat Knit Slip on Sneakers 6 36 NEW , Keen Presidio Women's Cascade/Shitake Shoes 10.5M , Womens Nike Free 5.0 TR Connect 2 Running Shoes 638680-007 Size 9 ,
"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."