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.JAMBU Leather/ Textile Water Ready Adjustable Toggle Sport Sandals Wm 9.5 , MERRELL "ERA" Women's Size 7 M Taupe Suede Leather Slip-On Walking/Trail ShoesNaturalizer N5 Comfort Women’s Flats/Loafers/Moccasins Size 9 Narrow Black , Prada navy blue Leather Slip On driving Loafers Italy Size 37Jslides Aztec Shoe - Women's Size 8.5 M, Pewter (Damage)RARES chaussures THERESIA M MARRON BRONZE T 38 TBE A ACH IMM FP RED MOND REL , Clark’s Wmn Artisan Ruthie Twist Clog Black US Size 6.0MNAOT BROWN BRONZE LEATHER WEDGES CAP TOE SLIP ON LOAFERS SHOES WOMEN'S 40 L 9Naturalizer Novara Loafers-Women's size 8 M Black , baskets montantes femme marque PUMA point 39WOMENS CLARKS COLLECTION CUSHION SOFT COMFORT BLACK LEATHER WORK SHOES SIZE 11MNIKE VIEW III 3 WHITE/PALE BLUE WALKING Womens Size 8New Balance? ~ 412 Trail Run Shoes ~ Everyday WTE412P1 ~ Women Sz 6.5 ~ VGSperry x Gray Malin Beach Print Sneakers Mens Sz 5 Womens Sz 7 Tropical Ocean , NEW $74 Womens Puma Vikky Platform Ribbon shoes, size 11 , White Low Top Converse All Star Tie Tennis Shoes size 7 Elastic Backsadidas Women's Aerobounce ST w Running Shoe - Choose SZ/Color , New Balance 574 Pique Polo Trainers in Pink & Navy WL574 POP Naturalizer Morrison Leather Fashion Sneakers, Women's Size 8N, Black , 7.5 WOMEN'S Nike Air Classic Cortez RUNNING CASUAL LIGHT SHOES White Black PINK , Womens New Balance 574 6.5 Blue Sonic Ale WL574ALE Orange Yellow Bright SneakersNew Saucony Triumph ISO 2 Lady Runnng Shoe/Gray-Blue-Slime $149 Runners WorldSkechers Street Women's Double Up Fashion Sneaker , SAUCONY JAZZ ORIGINAL WOMEN'S SIZE 7 RUNNING SNEAKERS MODEL S2108-627 New in Box , Vans Iso 2 Rapidweld Women's Size 8.5 Perf Delicacy White Pink OTW RareNew The North Face Womens Storm Tr Gray Running Shoes Size 10.5GUESS Sneaker Tennis Sport Athletic Walking Shoe Shoes Flip Flop NIB 6 7 8 9Brahma steel toe shoes Woman's size 6Skechers size 9 womens relaxed fit memory foam white shoes athleticAdidas Womens Vigor Bounce F16/UtilityBlueF16/IcePurpleF16 Running Shoes Size
"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."