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 Canvas Mule Slip On Shoes Flats Slides Open Back Sandals Casual BacklessWomen Wedding Shoes Flat Heel Pointed Toe White Black Shoes Pumps Slip On CasualWomens Black Loafers Shoes Ladies Slip On Diamante Office Work School Pumps , NEW BALANCE COBB HILL CAG28BK women's 6.5 black leather Mary Jane comfort shoes , Rockport Women's Size 7.5W Loafer Slip On Suede Leather Tan Nice Soles W8769 OD , Women’s Ballet Cushion Flat Slip on Shoes Black Beige , Cream & Gray Snakeskin Pattern LL BEAN Elasticized Edge Flats 10 M , Women's Franco Sarto Flats - Roland - Camel Suede - New in Box!! , ARIAT WOMEN'S US 8B 93601 DEL MAR BLACK LEATHER HORSE BIT CLOSED CLOGS A7 , MUNRO AMERICAN WOMEN'S LUNA BLACK SHIMMER ROUND-TOE FLATS - NEW SHOES- SIZE 7.5N , HUSH PUPPIES Tartan Plaid Red Black Oxfords 7 , SAS Womens slip on shoes size 7 MBrowns Women's Genuine Leather Flats 0132684 Size US 8.5Born Womans Flats Size 8 39 Brown Leather Sticky Strap Loafers , Avec Les Filles Womens Gisella Closed Toe Espadrille, White Floral, Size 7.5 y9x , STEVEN by Steve Madden Womens arden Closed Toe Mules Grey fab Size 7.5 8Zn5Ariat Women's Brown Leather Slip On Loafer Clogs Cap Toe Heel Shoes 9.5 B 40.5 , Nike Free Womens Sneakers Shoes Size 12 Turquoise White Silver Running Shoes A30 , Dr Comfort Womens Shoes Pink Blue Gray Athletic Sneakers Refresh Size 9XW , Merrell Allout Shine Greyt Walking Shoe Women's US SZ 5.5 J55212Women's LPB Ballerine Ella Metal Argent Surprise Flats , NIKE Wmns Ultra Comfort Thong 882697-100 WHITE/BLACK-WHITE Womens SZ 8Skechers Women's Go Flex Max Strength Walking Grey 8 B(M) USAltra Shoes Zero Drop Youth Size 4.5 Womens Size 6 , New Balance WL555 Women's Only Casual-W Womens- Choose SZ/Color.ASICS GEL-Flux 5 Blue - Womens - Size 11 B , New with Box Nike Women Flex Supreme Training Sneaker, sz W10, retail $80New Balance Women's Wbre Ankle-High Running Shoe , K-SWISS Womens White Athletic Shoes Size 6.5 style 60440 , Women's Puma Prevail Heart Sneakers, New White Gold Sport Runinig Shoes Sz 7.5 ,
"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."