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.Dark Brown Leather BASS Backless Slides w/Weaving Cord & Tassles 6.5 MLUCKY BRAND Size 6.5 Erin Metallic Ballet Slipper Flats ShoesLiterary Womens Girls T Bar Block Heels Hollow Strappy Shoes Tip binding Sandals , STUDIO WORKS 9 M FUSHIA PATTEN PINK BOW CASUAL WORK PARTY FLAT SHOE , BORN TAN SUEDE LEATHER SLIP ON CLOG WOMENS SHOE SIZE 9(US).EUROSTEP - TAN LEATHER KNOT-TASSEL LOAFERS/FLATS - LADIES 8M , DKNY Jillian Donna Karen New York Slip On Women's Sneakers Shoes Athleisure GrayWhite Mountain SHOES WOMEN'S SIZE 7 MAravon Size 13 AA Black Shoes Women's - No Insoles , Womens MINNETONKA mocs size US 10 M red leather flats shoes casual shos FREESHIPTods Dark Gray Square Toe Loafers Flats Size 7.5 , Merrell womens primo patch brown bug shoes size 8.5 USDansko Nanette Mary Jane Shoes Womens Size Eu 39 Black Leather Shoes NO INSOLESAlegria by PG Lite Womens Paloma Black Rose Patent Mary Jane Shoes Size 35/ US 5Rocket Dog Pompeii Heather Fabric Womens Flats- Choose SZ/Color. , Adidas Climacool Women's US Size 9.5 Black Grey Pink Shoes Running Cross Fit S18OluKai Womens Eleu Trainer Athletic Breathable Cushioned Water Shoes Size 7.5 , ORTHOFEET Orthotic SPRINGFIELD Spandex MARY JANES NAVY Women's SZ 5 XXWLADIES SHOES/FOOTWEAR -Cherry Shoes Merle pewter , Mens Slides Beach Flats Slip On Summer Casual Home College Sandals Slippers Hot , Reebok Women's Walking Tennis shoes Gray Blue Size 9.5Skechers Womens 15600 Go Walk Joy Low Top Slip On Walking, Black/White, Size 5.5CONVERSE All Star Low Top Khaki Beige Black Shoes Womens 7.5 Med Sneakers CanvasSkechers Performance Women's Go Walk Slip-On Walking Shoe (Size 7) , Primo Distressed Vans Lo Top Slip On Shoes Black Splatter 5.5 Mens 7 Womens , Saucony Womens Sapphire Running Shoe- Pick SZ/Color. , NIB Womens Size 7 Vionic Mckinley Gray Lavendar Trail Hiking Shoes New , NIKE AIR JORDAN 11 XI RETRO LOW Pink snakeskin snake skin Size 9 womens sz 7.5 , Skechers Sport Women's Skech Air 2.0 City Love Fashion Sneaker , Bentheim Black Pied Pig Christmas Running Shoes For Women- Free Shipping ,
"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."