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.NEW Womens SODA POTION Black Round Toe Casual Slip On Linen Sneaker Flat Shoes , Stuart Weitzman Black Patent Leather Peep Toe Flats Shoes, Size 8.5 , BALLERINE FEMME NOIR PETIT NOEUD SEMELLE INTERIEUR CUIR POINTURE 40Liz Claiborne Blue Canvas Sneaker Slides Women Size 6 May also fit Youth 4/5Steve Madden Women's Lynn Zip Sneaker, White Leather, 7.5 M USSloggers Women's Blue Slide On Shoe Moisturizing Wicking Thermal Insole Sz 9 ✞ , $135 Ecco 37 6.5M dark brown womens ladies flats loafers comfort shoes , Aerosoles Sawcremento Mule Shoes 132, Dark Tan Combo, 7 US , Stuart Weitzman Womens Flats Size 7.5N Black Embossed Leather Loafers , Franco Sarto Womens Flats Avice Silver Bow Pointed Toe Slip On Career Size 7.5 , Nine West Women's BAUS Driving Style Loafer, Gold, Size 9.0Spanish TAOS Step It Up Size 7-7.5 (38) Blue Pin-Perfed Embossed Mary Jane Flats , Women’s Sperry Top Sider Black Sparkle Shoes Size 11Jessica Simpson Womens praylee2 Closed Toe Classic Pumps, Champagne, Size 9.0 yXTORY BURCH Black Leather Eddie Ballet Flats Slip-On Shoes 7 M Great-Clean! $150New Balance Women's W562 Grey/Lime/White Running Sneaker 7M , Womens Black Suede NEW BALANCE 442 Low Sneakers Shoes Sz 5.5 BKeen Leather Mary Jane Strap Comfort Walking Casual Shoes Brown Size 9 USFila Ladies Memory Showcase 3 Tennis Athletic Running Shoes Size 6 6.5 7 8.5 , Report Women's Abe Fashion Sneaker - Choose SZ/ColorNew!! Women's Skechers Flex Fit - Walking Shoes Black style 11662 F32Women's Reebok Crossfit size Women’s 6.5 Durability Athletic Shoes , Women's Fergalicious Women's Jiffy Sneaker We Have Won Praise From Customers Athletic ShoesWomens SpeedForm Apollo Running Shoes Trainers Black Pink 1245955 002 U1 , EUC Women Nike Air Max 95+ BB 511308-013 Size 6.5 blue grey , ASICS GEL-Flux 4 - Blue - WomensNike Wmns Air Max Siren Print Polka Dot Red Women Running Shoes 749511-602NIKE PRIMO COURT TENNIS SHOES FIREBERRY WHITE WOMENS WMNS SZ 6-10 631635-612New Converse Chuck Taylor All Star Dainty Low Top Women Sneakers , Skechers Sport Women's Flex Appeal Rival Cross-Training Shoe Wide 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."