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.Fabulous "UNISA" PURPLE LEATHER BALLET Pumps Shoes , Circus by Sam Edelman Ciera Bow Ballet Flats Size 10 M Classic Red LeatherESPADRILLES P. 34 PICHOTO "Né en Provence, Fabriqué en Espagne " PRIX MAGAG.H. Bass & Co. Wynn Mules 966, Black, 6 US , Prada Sport Leather Slip-on Womens Made N Italy Size Eu 38.5 Us 8.5 , Born - Womens - Tami Tan Leather 8 (M) US , Womens Skechers Bobs Plush Go Fetch Black Slip On Shoes [32574/BLK] , Munro American Mallory Black Leather Slip On Loafers Womens Size 10.5 M* , loafers Prada chaussure cuir verni noir 38 moccasinsSkechers Go Walk Lite Daisy Black Bbk Womens Slip-On Size 7MWomens 7.5 Nike Revolution 2 Shoes 554900-006 RunningRestoration Hardware Mens Large Pair Cashmere Scuff Slippers Charcoal Grey 10,11 , Stafford Mens Slippers Memory Foam velour cover indoor outdoor size M L NEW , Saucony Womens Feel Sneaker- Pick SZ/Color. , New Keds Womens Wh55804 Black Fashion Shoes Size 5 , CHAUSSURES MONTANTES 100 % CUIR ROUGE ELISABETH STUART COMME NEUF ! P 39 / 40 !Women's Easy Spirit Women's Davet Mule Selected Materials Flats , Women's robert zur womens shoes Sale Price Flats , Nike Wmns Air Zoom Structure 19 Hyper Violet Blue Women Running Shoes 806584-500 , VANS Sk8 Hi Slim (Pop) Columbia/Black WOMEN'S Skate Shoes 10.5NEW New Balance Women's 910GX3 910v3 Trail Gore Tex Black Running Shoe Sz 6 BGrasshoppers Women's Stretch Plus Hook-and-Loop Sneaker - Choose SZ/ColorSkechers Women's Nampa-Annod Food Service Shoe - Choose SZ/ColorHoka One One Clifton 2 Womens Size 10.5 Gray Pink Running Shoes Ortholite F7 , Nike Lunarstelos Lightweight Running Shoes Women's Sz 7.5 - Blue - Fast Ship! , Dr. Scholl's Women's Scout Slip on Fashion Sneakers - Silver - Size 8 M , Adidas White Blue Leather Mesh Running Training Shoes Women's US 10ASOS Dandelion Purple Pom Pom White Sneaker, High Top, Size 7 , Women's Nike Lunarglide 5 Violet Frost Purple Gamma Running Shoe 599395-545 Sz 9 , Converse Womens Chuck Taylor All Star Madison Ox 555910F Size us 5-M NWOB ,
"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."