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.**Skechers BOBS Plush Peace And Love Slip On - Women's Size 5.5 - Blue , Alegria mary janes 41/ 10.5 / 11M brown comfort , LADIES "AMERICAN EAGLE" MULTI-COLOR COTTON SLIP ON LOAFER SHOES 9.5M , Nine West Womens Wedges Size 9.5M Open Toe Canvas Buckle Brown -3755EASY STREET SPORTSTER Slingback Comfort Croc Print Brown Loafer Sz 7 M Women's , Cole Haan Grand OS Women's Snake Skin Ballet Flat Wedge Heel Shoes Size 7.5BareTraps Aimelia Ballet Flats - Women's size 8M - BlackSAS womens shoes Roamer 9 N mary jane comfort navy blue leather Tripad T-strapMERRELL PEFORMANCE FOOTWEAR BLACK SHOES MARY JANE SPIRE EMME SIZE 10Alexander Wang Suede Strappy Pointy Toe Flats size 40Clarks Brown Suede Mary Jane Tamitha Aster Comfort Shoe 7.5 New , Aerosoles Good Times Flat - Women's Size 8.5 Wide, Dark Grey Suede , Dr DOC Martens Made in England Womens SHOES 10 US / 8 UK Leather 8065 SandalsSeaVees Womens 09/64 Yosemite Hiker Leather Gray Casual Sneaker Shoes Size 8 , Easy Spirit Womens Twist2 Closed Toe Loafers, Porcelain-white, Size 8.5 jnSu , Easy Street Women's Splendid Flat, Stone, 6 2E USFashion Women Sneakers 2018 Breathable Waterproof Wedges Platform Shoes PuWomens Summer Mesh Sport Sneaker Breathable Flat Platform Athletic College ShoesIsotoner Men's Microsuede Memory Foam Moccasins brown Slippers SZ XL (11-12) , New Keds Womens Wh55804 Black Fashion Shoes Size 5Womens ADIDAS ELEMENT REFINE TRICOT W Lime Running Trainers M21533 , Under Armour Women's Jet Basketball Shoes US Size 6 Black/ Pink 1259035-064 MINTMERRELL Kangaroo Mimosa Glee Hiking Trail Womens Shoes Sneakers Sz 6 M J46584 , Merrell Womens Jungle Moc Sport Berry/Grey Trail / Hiking Shoes Size 6.5 (C,D,W)New Merrell J09648 Bare Access Flex Aruba Blue Women's Running Shoes 10 USTEVA SPORT Hiking Shoes 6034 Water Sport Brown Suede Slip On US 5 $89.95Brand New Authentic Birkenstock Gizeh BS - Stone - Women's size 8Vionic Elation Lightweight Running Shoes, Women's Size 6, Red/Yellow/PurpleNIKE WOMENS FREE RN FLYKNIT 2017 ATHLETIC SHOES [880844 400]Skechers Stretch Fit Kiss - Secret Black Air Cooled Memory Foam Shoes NWOB 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."