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.6 1/2 WORTHINGTON FLATS Croc LINDA Womens Sz 6.5M BLUE BELL Escada Loafers shoesSam Edelman Caper Brown Suede Rhinestone Ballet Flats Shoes Size 8M , Charles Albert Size 6 Red FlatsME TOO Women' Shoes wedge Loafers, 11 M, BROWN LEATHER , Lady Godiva Women's Boat Shoe Flat String Tied Moccasin Loafer Brown Size 8Marc Jacobs Womens Black Satin Espadrilles Flats 10 Medium (B,M) BHFO 2357Ballerine chaussure plate femme loafer sandale babies mocassin CUIR 41 NEUFKlogs Cardon Women's Leather Clogs Display Model Shoes Black Wigwam 8 M , Quoddy Moccasins Ladies 8M Worn Only a Couple TimesNine West Adley 7.5 Flats Metallic Silver Flats Pointed Fashion Work Loafers NewSAS Tripad Womens Shoes SZ 8.5 S Pearl Navy Blue Leather Loafers Comfort Flats , GB35 Jileese Casual Loafer Flats 413, Black, 9 USSeaVees Baja Casual Slip On Shoes - Women's Size 7, Black LinenWomen's Sandals barefoot skin soft shoes swimming shoes snorkelling shoesDONALD J PLINER GREEN SUEDE POINTED TOE LOAFERS W/ ORANGE COW WOMENS SIZE 6.5 M , Adidas Daroga Climacool Brown Running Shoes 791001 - Women's Size 9Brooks Womens Ghost Running Shoes Sz 8.5 , SKECHERS Empire Game On Sneaker - Women's Size 9 Multicolor , Women's Merrell Meta Strech Brown Loafers Crazy Price Athletic ShoesWomen's tory burch shoes size 5.5 Quality And Quantity Assured Flats , Reebok Women BD5321 Royal Glide Ripple Clip casual Shoes white sneakers , New Olukai 20271 PG26 Pehuea Pale Grey / Charcoal Women's Slip On Shoes 7.5 USNew Balance WT1210SP Women's Leadville 1210 Ultra-Runner Running Shoesnike womens flex trainer 4 running trainers 643083 603 sneakers shoes CLEARANCE , New Balance Womens Asparagus/Pink Running Shoes Size 10.5 (20255)Big Sale!! Vans Sk8-Hi Reissue VN0A2XSBLYW Men/Women shoes Fast Shipping size5 O , VANS Authentic (Guate Stripe) Red Mahogany/White Casual Shoes WOMEN'S 9Newton BOCO AT ll Running Shoes Blue, Lime, Yellow Women's US Size 5.5 (E2,2) , New Balance 490V5 Size 7 B Women's Running Trainers Shoes Sneakers Black W490LI5ASICS Women's fuzeX Lyte Running Shoes T670N
"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."