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.Handmade New Indian Jodhpuri Pure Leather Pom Womens Ethnic Casual Ladies jutti , Wanted Rumors Ballet Flats 546, Tan, 8 US / 38 EU , Clarks Springers Womens Black Leather Slip On Size 7M Thick Sole - 3050FRANCO SARTO Size 7.5 ELEGANCE Black Leather Ballet Flats Shoes 7 1/2Women's size 7.5 5092 SPERRY TOP-SIDER Leather Plaid Boat Shoe Slip On Loafer , MERRELL Plaza Bandeau Leather Suede Mary Jane Heels Womens Size 7 Espresso BrownDansko Oxford Platform Brogue Toe Womens Black Leather Shoes Size US 7.5-8 , Keen 1006616 Catalina Women Size 9 Red Canvas Boat Shoes Loaferschaussures mocassins en cuir et vernis marron ara t 38 vintage , Clarks 'Candra Gleam' bronze leather square toe slip on knotted flats 7M 4956 , Aerosoles Womens Trend Setter Leather Closed Toe Loafers Black Suede Size 6.0NIB Women's Guess Jaida Metallic Leather Fashion Sneakers in SilverBernice Spring Step L'Artiste Collection Women's Sandals Grey Multi US 7Eastland 3180 Women's Leather Slip On Loafers Size 9w BrownSKECHERS PREMIERE WOMENS BLACK SLIP ONS SIZE 7 1/2 , Animals Pug Dog Women Sport Breathable Sneakers Casual Running Walking ShoesWomen's Josef Seibel 'Caspian' Leather Comfort Sneakers Gray Size Euro 40NEW Women's SKECHERS Black Bungee Slip-On All Day Comfort Exemplary Shoes 8 US , Women's LifeStride Women's Ginja Slip-On Loafer Fashionable And Attractive Packages Flats , New Olukai 20271 DEDE Pehuea Trench Blue Women's Slip On Shoes 7.5 USYorkshire Blue White Print Sneakers For Women-Free ShippingVANS Court DX (Leather) Black Skate Shoes WOMEN'S Size 7Saucony Grid Ramble TR3 Womens 7.5 M Running Shoe Sneaker S15230 Black Teal Blue , New Balance 627 Women's Industrial Steel Toe Slip & Oil Resistant Shoes Size 11New Nike Womens Duel Racer Run Running Shoes 927243-201 sz 8.5 String-ChromeBrooks Addiction Walker Shoes White 8 2E EXTRA WIDE Aftermarket Insoles , New Women's Skechers 11931 D'Lites Fresh Start Sneakers - Black Size 6 (E12) , Converse All Star Chuck Taylor OX 551547F Women ShoesWomen's Saucony Excursion TR10 Gray/Blue/Coral Trail Running Shoe Sneakers , Skechers Women's Reggae Fest-Marlin-Fisherman Open Back Mule, Charcoal, Size 8.5 ,
"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."