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 BALANCE white walking "fit walk" shoe "Strike Path" - size 9BWomen's Drew P246 Last Tan Leather Slip On Mules Shoes Loafers Size 7M , Steve Madden Womens Shoes Size 10M Snake Skin Pattern Ballet Flats Slip Onwomens anne klein cailley multi colored leather skin print loafers shoes size 7 , Beacon Terri Women's Slip On, Multi-aztec, Size 8.5 bDjL9 M | Clarks Bendables Bingo Women Tan Leather Slip On Flat Clog Loafer Moc , holster Australia Shoes - Comfortable Vegan Ladies Leo Slip-on Sneaker - Silver , Steve Madden Women's Limit Fashion Sneaker Black Size 11.0 , Asics Gel-Excite 2 Womens Lightning/White/Turquoise Running Shoe 12M , Vintage canvas tennis shoes Lacrosse SCAMPS women ladies teen navy blue sz 5MPuma Suede Platform 36222302 Blue White Casual Shoes Medium Women Sz 9 , Women's Tennis Shoes Champion Athletic Size 9.5 Ladies 9 1/2 Sporting Goods , Birkenstock Footprints Suede Leather Sandals Mary Janes Women's 41 / 10 GermanyPatrizia by Spring Step Women’s Black Slip On Lightweight Loafer sz 40/9 NEWWOMENS NEW BALANCE 677 CARDIO COMFORT LIGHTWEIGHT SHOES Sz 9.5 , ASICS Gel Lyte III Red Metallic Running Sneakers H6E5K Women's 6.5 /**Rockport Truwalk Zero Sneaker- Women's Size 6 M, GreySteve Madden Womens Felecia White Fashion Sneakers 11 Medium (B,M) BHFO 6133Women's Merrell Pace Glove Running Shoes Size 6 US , Nike 724850 Womens Roshe One Breathe Low Top Running Athletic Shoes Sneakerswomen's shoes BEVERLY HILLS POLO CLUB 9 sneakers multicolor suede AH997-FNew Sperry STS82436 Oasis Canal Navy Blue Women's Boat Shoes 6 US , adidas Adilette CF Plus Womens Vapour Grey Met/Vapour Grey Met/Core Black B75679 , NIKE Womens WMNS Downshifter 7 Aluminum Black White Size 7.5Steve Madden Glacier Sneaker, Women's Size 7 B, BlackConverse All Star Sneakers w/ Swarovski Rhinestones Multi Colored NEW You PickNew Womens Skechers Skech-Air Infinity New Heights Shoes 12175 Black\White 16CPUMA Women's BASKET CLASSIC CITI METALLIC Shoes Copper/White 364165-01 a , 15600 Burgundy Skechers shoes Go Walk Joy Cool Women Mesh Slip On Comfort Casual“BALLY ALESIA mdl” copper-brown leather sneaker-drivers; 39EU/8.5US, Switzerland
"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."