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.Report Signature D'Orsay Flats Shoes Brown Leather Womens size 7.5 , Softspots Venus Lite Oxford Taupe Womens Size 6Cole Haan Womens Brown Woven Slip On Flat Leather Loafers Sz 7B F3137Ryka Nitracel Brown Arctica Suede Leather Faux Fur Lined Slip Shoes Clogs - 7.5MCROCS MALINDI FLAT SLINGBACK WOMENS BROWN US SIZE 4 M NEW WITH TAGS , LEATHER BALLET JIFFIES Lauren Womens Dance Flats Shoes Black Red Camel Tan 5-10~G.H. BASS & Co.~ 'Sandy' Blue & White Striped Casual Fashion Sneakers/Shoes 8.5 , CLARKS EUC Women’s brown Leather slip on Shoe Sz. 9 1/2 , Enzo Angiolini Womens Liberty Coral Orange Slip On Loafer Flats Sz 8 M , Sanuk BLANCHE Womens Sidewalk Surfer Slip-On Shoes Size 7 Eggshell NEWSanSidewalk Surfers Womens Pick Pocket Fleece Flat- Pick SZ/Color. , Women's Crocs Slip On Shoes Model:16211 Size W10 Pink w/ White Soles , Dakota Quad Lite ATCP Women's Black Athletic Shoes 9.5W , Women’s SIZE 9.5 NIKE FLEX EXPERIENCE RN 3 Running Shoes , Saucony Grid Profile Running Shoes, Black/Pink/Silver, Women's US Size 7Women's Power Light Athletic Running Shoes Sneakers Size 6.5 White & Teal , Clarks Women's Leisa Sadie Clog , Naot Mary Jane Green Women's Size 39SAUCONY Excursion TR7 Trail Running Women's Shoes Size 39 / 8New New Balance Womens Wrushpb2 Black/AlphaPink Running Shoes Size 5.5Dr. Scholl's Madi Jute Slip On Sneaker-Women's Size 7.5 M, Oxide Microfiber Perf , Skechers Performance Women's Go Joy 15601 Wide Walking ShoeBlack/White8 W US , Women's Skora Fit Minimalist Running Shoes Size: 9.5 PinkASICS Womens - DivaBlue/Silver/Orchid Running Shoes Size 8 (361387)NIKE WOMENS ZOOM CONDITION TR INDIGO TRAINING SHOES (BOX NO LID) , Converse All Star Chuck Taylor OX 159545F Hyper Blue Women Shoes *NO BOX , Merrell Siren Sport Gore-Tex Hiking Shoes Women's Size 8.5 EUC , Merrell Womens Siren Edge AstralAura Trail / Hiking Shoes Size 6.5 (413109) , Skechers Women's Burst - Fine Vines Ankle-High Fashion SneakerHoka One One Women's Constant Blue Atoll/Neon Coral Running Shoes 10M ,
"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."