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.Ariat Womes Clog Style Black Sz 10Women's Black Leather DANSKO Mary Janes Size 40, US 9.5 - 10 M Great Condition , Ladies slip on casual shoes by eaze red , man made,elastic fitting upper F9436Rockport Brown Leather Stitched Wedge Loafers Shoes Womens Sz 9.5 MJ. Crew Olive Green Patent Leather Flats Size 7 NARROWMerrell Jungle Moc Classic Taupe Womens Shoes Size 7.5 Suede Slip OnSofft Women US 8M Brown Leather Loafers Slip On 2" Heel Clogs , J Slides Women's Pollie Sneaker, Black, Size 10.0 , Easy Street Womens Effie Closed Toe Loafers , Nine West Womens marie Leather Closed Toe Ballet Flats, Black/Pewter, Size 8.0 , Cole Haan Womens Willowsam Suede Closed Toe Oxfords, Tawny Port, Size 6.0 Tzx0 , Lucky Brand Archh Women's FLATS Black/Grey , NEW Rockport K59933 Shore Bets Seaworthy II Leather Loafers, Women's 7M, Navy , **Crocs CitiLane Roka Slip On Shoes, Women's Size 10, Black/White NEW , Cacey Black Leather Me Too Flat Mary JanesNike AIR FORCE 1 '82 Women's Size 7 Y Athletic Shoes 031012 Black Leather Upper , UNIONBAY Women's Shtng Str Fashion Sneaker, White, 9 M US , PRIVO by Clarks leather shoes size 10 m strap fashion, cushioned comfortNike Training Flex TR 5 Black Running Shoes Womens Size 7 724858-001Nike 9.5 Black And White Sneakers WomenNEW Adidas V Racer 2.0 W Womens Casual Classic Shoes DB0424 White Beige Size 7.5 , Keds Women's Champion Oxford Canvas Sneaker Black/BlackBrooks Womens 120246-451 Navy/Pink/Teal Green Walking Shoes Size 8.5 (30134)Vionic womens shoes orthaheel size 7ASICS GEL-Fit Sana 3 - Blue - WomensAdidas Women Tubular Viral orange easy orange energy orange footwear white BB206Merrell Boulder Womens 8.5 Coral Vented Hiking Performance ShoeNEW Womens 9 NIKE Zoom Rival MD 7 Pink Orange Mid Distance Track Spikes Shoes , Adidas Womens Lite Racer Black/WhiteTextile Running Shoes Size 6.5 (359621) , Nike Free RN (GS) Youth & Wmns Running Shoes Various Sizes 833993 100 Turquoise ,
"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."