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 Without Box Quacker Factory Christmas Package shoes size 7 1/2 M , Hirica Womens Flats Size 39 9 Tan Leather Bow DetailAravon Women's Revsavor Waterproof Slip On Sneaker , Black Size 9 EE WideSperry Topsider Womens Tartan Plaid English Waterproof Rubber Duck Shoes Size 7MCroft & Barrow Pattieice Marilla Women's Memory foam Ballet Flats Shoes Sz.6AZAM Womens Classic Faux Suede Nubuck Penny Padded Insole Loafers Black , Dansko Clog size 39 Mules Shoes Slip On Slide professional Black Womens US 8.5-9 , Clarks Womens Black Patent Leather Loafers Croc Print Sz US 8.5 , FitFlop Pop Skate Perf Women's Slip On Shoe, Black - US 5Easy Spirit ACTIONPLANT Level 1 Black Mary Jane Shoes Size 9 NEW , Spring Autumn Loafers Women Shoes Ladies Flat Shoes Ballet Flats Woman BallerinaCLARKS Women's Size 9 1/2 M Black Leather Slip-On Clog MulesGenuine SAS Womens Leather Handsewn Loafers Shoes Sz 7N / 37.5 EU Soft Step Heel , FITFLOP Black Suede Clogs Mules Shearling Lined Womens Shoes Size 5 106-001RARES CONVERSE MARRON CHOCOLAT T 39 EN BE A ACH IMM FP RED MOND RELAY A VOIR , Speedo Seastride Surf Knit Water Shoes Women's Size 8 , COLE HAAN yellow womens Grant Horsebit Driver Mocs Slip On Loafers Size 9 , Brooks 1S Adrenaline GTS Women's Running Shoes Size 8.5 Blue with Pink/Neon Trim , NORTHSIDE MEN'S MANCHESTER SLIP ON SYNTHETIC INDOOR OUTDOOR SLIPPER SHOE US 9Kenneth Cole Womens 5 Brown Leather Grunge Skater Prep High Top Shoes SneakersNike Zoom Soldier IV Lebron James Basketball Athletic Fitness Shoes Women Sz 10ASICS GT 2110 WOMEN'S ATHLETIC RUNNING SHOES SIZE 9 BLACK GRAY TN654Bearpaw Women's Opal Slingback Wedge Sandal Tan Synthetic Sandals , Women's Adidas Gazelle Casual Sneakers Size 7.5 Very Nice!!!Adidas Women's Lifestyle Casual Shoes 145609 SAMOA L W - Women Size: 9.5 Only DS , Chihuahua and Black Dots Print Running Shoes For Women-Free ShippingASICS GEL-Excite 3 - Pink - Womens , Brooks Ariel 16 Womens Sz 7B Med Blue Teal White Mood Indigo Running Shoes NiceHoka One One Mafate Speed Women's Grey/Black/Fuschia Running Sneaker 7M , FILA Cool Max Memory Foam Blue Purple Pink Women's Sneakers Shoes 7.5 New In Box
"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."