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.Teva Nylon Ankle Straps Flat Slingback Shoes Sz:8 M US/39 EU/6 BuckleMinnetonka Shoes Size 7.5 Brown Solid Suede Leather Flat Slip On MoccasinsNot Rated Womens Trenoly Mesh Gray Slip-On Shoes 8.5 Medium (B,M) BHFO 8162 , LC Lauren Conrad women Blush cute Flats pom pom accentPedro Garcia Gold Textured Leather Ballet Flat Shoe Sz 35.5 5.5Bare Traps Womens ALYSON Closed Toe Slide Flats, Black, Size 7.0Simply Vera Vera Wang Cream Colored Beaded Embellished Svanitanatural Shoes 9.5Nine West Womens 7Zavanna Leather Closed Toe Ankle Wrap Slide FlatsYosi Samra Vera Flats - Women's Size 6, Black , Vaneli Womens Mambo Wedge (B)- Pick SZ/Color.Klogs Missy Women's Leather Clogs Display Model Shoes Mahogany 8.5 M , Womens Leather Slip on Loafers Bowknot Korean Mary Janes Party Oxfords Pumps newNIB Nine West True That Pointy Loafer Shiny Black Color Size 6.5 Medium All New , (A-8 ) Brooks Asteria Women SIZE 7.5 Medium (B) Running ShoesOrthofeet Gel Red Leather Walking Casual Mary Jane Womens 12 M Shoes Comfort EUCSKECHERS SHAPE-UPS silver,white,blue 9.5M in excellent condition , Fila Windshift 15 Ladies Running Athletic Shoes Size 8Brooks Glycerin 10 Running Sneakers-Training Gray/Pink Athletic Shoe Womens 8.5B , BROOKS Womens Ravenna 4 Running Sneaker Shoes Walking Size 8.5 Teal Blue , Size 13 M By Susina Slip on Sneaker Style , $90 Size 7.5 Merrell Encore Brown Suede Bracken Shoes Slip Ons Sandals , Nike Air Max Thea Ultra FK Flyknit Running Shoes Women Multi-Color US 5.5Womens New Balance 574 Shoes WL574OIB Size 7 , Kenneth Cole New York Women's Kiera Double Zip MID-TOP Sneaker VelvetSkechers Women's Comfort Flex Sr Hc Pro Health Care Professional ShoeASICS Gel-Nimbus 15 IGS Women's Size 10 Running Shoe Green/Pearl /Yellow T3B5N , Hi Top Shoes Multicolor Pink Blue Teal Purple Silver Glitter Size 6 Airspeed , SKECHERS WOMENS MICROBURST SPIRITED MEMORY FOAM 23306/BKWWoman Rainbow Flirty Braidy Single Layer 301ALTSB Sierra Brown 100% Original NewNew Balance 786v2 Sneaker - Women's Size 7.5, White/Navy
"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."