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.Women's Flats Ladies Heart Comfy Shoes Soft Slip-On Single Casual Boat Shoes , sperry topsiders kelly green blue leather flat boat shoes 7 , Ryka Womens Size 8 () Brown Hook and Loop Strap Mary Janes , Women's Naturalizer Burgundy Block Heel Leather Loafers US8MClean GreatCondition , Karl Largerfeld black studded wedge flats shoes sz 8.5EUC Sacha London Beige Suede Ballerina Flats Open Toe US 10ECCO Light Brown Leather Bicycle Toe Shock Point Loafer Womens Size 36 US 5/5.5Minnetonka Deerskin Beaded Moccasins Flats Kilty Slip On Loafer WOMENS SIZE 11Sperry Top Sider Womens Boat Shoes Firefish Animal Tan LeopardSkechers Seager - Prospect Black Bbk Womens Sneakers Size 6MNEW Size 6.5 G.H.Bass Women Shoes Moss Suede Model: Leslie Leather Suede GreenSKECHERS Imprint-Serrano 46110 Womens Brown Leather Suede Casual Shoe SZ 7.5 S60Red Women Lady ALL STARs Chuck Taylor Ox Low Top classic Canvas Sneakers US7.5 , Josef Seibel Women's Minu Leather Flat Bronze Dress Slip-On, Size 37 EU, 7 US , Stuart Weitzman Black Suede Ballet Flats sz 6 NWOB , Womens Increase Thick Sole Hollow Out Grenadine Sport Shoes Casual Shoes A201Everlast Womens Memo Tech Black Pink Sz 8.5M Layla Sneakers Low Cut WalkingCoverse All Star Chuck Taylor/Woolrich Hi-Top Womens size 6 , PUMA Women's Vikky Sneaker Cerulean Blue-Puma White Suede Leather Casual Shoes , Skechers Sport Women's Flex Appeal2.0 Mixed Media SneakerBlue9 M US , Nike 407847-003 Womens Dual Fusion ST Running Shoes Sneakers Size 6 Gray PinkNEW $69 Womens Nike Flex Experience RN 4 Running Shoes, size 10 grey/blue , Prada Sport Shoes Athletic Blue And Grey womenPUMA 36556102 Womens Suede Heart Celebrate WNs Sneaker- Choose SZ/Color. , Steve Madden Women's Gills-p Sneaker, Natural Suede, Size 7.0Women’s Nike Shox Athletic Running Shoes Black Orange Grey Size 8.5 , Vince Blair 5 Casual Slip On Shoes - Women's Size 6 M, BlackAdidas Stellasport Women's Size 8.5 Irana 2 Cross Trainer Shoes Gray White, PinkNew Balance Women's 990NV3 Running Shoe (Navy) , Skechers Women's Go Step Lite-Streak Walking Shoe Black Size 7.5 YmIq
"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."