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.7811963 LSP30 Women's Shoes Size 7 M Beige Suede Slip On Johnston & Murphy , NEW WOMEN'S LANDS' LANDS END SLIP ON SHOE SIZE 6 M SUEDE MAROON SIDE BUCKLELADIES SPOT ON BUCKLE FRINGE VAMP SLIP ON BROGUE SHOE IN VARIOUS COLOURS F80108LADIES WOMEN CASUAL FLAT BUCKLE STRAP WORK/SCHOOL PUMP SHOES SIZE 3-8 , NEW - SPERRY TOP-SIDER Women's 'MARINER DOUBLE GORE' Slip-On BOAT SHOES - 5.5 , Easy Street GiddyII Ballet Flats, Bone, 6.5 W USScholl Orthaheel Galileo Womens Casual Active ShoesCall It Spring Womens ackerly Fabric Closed Toe Loafers, Black, Size 11.0 , NIB P.W. MINOR XTRA DEPTH WOMENS KRISTA MARYJANES SHOES CLAY 6.5BICON SHOES USA GENUINE LEATHER SNEAKERS 38 7.5 5.5 $250 WOMEN , GUC PRE-OWNED LADIES "ASICS GEL-VENTURE 5" RUNNING SHOES SZ 8.5 GRAY & PINK LOOK , Nike Authentic Sneakers Women's Size 9Winter Womens Slip On Flat Shoes Patent Leather Fur Trim Comfortable US Sz4.5-9Womens MUNRO 212994 sparkling black leather loafers shoes sz. 6.5 M NEW!Easy Street Women's Kacey Flat, Blue/Blue Print, 6 2E US , Saucony Womens Jazz Low Pro Retro Look Sneakers Shoes sz 7 G621 , Sam Edelman Women's Branson leather Fashion Sneaker black 7.mFila Women's Memory Foam Outreach Athletic Shoe Grey Size 11 SEE DESCRIPTION$75 NEW Osiris Nyc 83 Slim Skate Hi Tops Shoes 4.0 M White/Pink/BlackFoot Petals Women's Andi Classic Trainer Cushionology Sneaker, Grey, 6 Medium USWOMAN'S SZ 8 LEATHER LOAFER SHOES BY BOC BRONZE COLOR , Skechers Women's Empress Fashion Sneaker, Black, Size 5.5 iNTt , Nike Women's Flex 2017 Rn Ankle-High Cross Country Running Shoe White SilverNike Womens Free RN 2017 Running Shoes GG8 White Anthracite 880840-103 8.5 Green , Nike WMNS Roshe One Hyperfuse BR women lifestyle sneakers rosherun NEW blue , $119.99 Puma Women Fierce Strap - Swan black 189461-01Reebok Walking Shoe Cloudride DMX Sneakers Womens Size 8 Brand New in BoxAsics GT-2000 4 Womens Running Shoes Size 7 T656N Silver/Turquoise/Lime , DKNY Cusual Shoe Womens Size 8 Black Fashion Slip on ClassREEBOK NEW CLASSIC LEATHER AND SUEDE BLACK AND GREY WOMEN ROYAL CL JOG TRAINERS ,
"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."