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.Rocket Dog Scoop Sunny Women's Pink Canvas Boat Shoe 11M , Steve Maddens Mary Jane Women Leather Shoes Size 8 P-audreeAmerican Eagle Outfitters ladies size 7 brown oxford Slip on Low heel Strap**Propet Travelfit Flats - Women's Size 8 4E - Red , Skechers Women's Bikers Herb Garden Mary Jane Flats Size 8 20A , CLARKS Black Leather Croc Print Wedge Shoes Loafer Comfort 65473 Women 7.5 M NEWCushion Walk Memory Foam By Avon Size 7 Black , $140 MISS SIXTY MARLENE Cuoio Brown Suede Designer Slip On Loafers 7Halogen Kayla Leather Pointy Toe Flat Beige Women Sz 10 M 6003 , Dansko Burgundy Leather Open Back Mary Jane Clogs Mules 39 Women's US 8.5 9Cheeks Air Trac Trainer Athletic Shoes, White/Pink/Purple, 6 US UsedFlossy Arnedo Women's Classic Casual Summer Slip-On Espadrille Grey , Brooks Transcend Women's Running Shoes Sz 9.5 White and Light Blue Exercise , Women's Brown, Blue NIKE "Dart VI" Sneakers Size 9.5 M GREAT Condition , RYKA Womens Grafik Cross-Training Shoe- Select SZ/Color. , Saucony Grid Cohesion 10 Mens Gray Mesh & Synthetic Athletic Running Shoes 12 , Ryka Studio D XT Training Shoes - Women's size 8,5 M, White/Silver 979Women's skechers high top sneakers 2017 New Athletic ShoesWomen's Dr. Scholl's Women's Hermosa Mule 2017 New Flats , Women's Giuseppe Zannotti Flats 37.5 Various Styles FlatsWomens Skechers Flex Appeal 3.0 Satellites Lightweight Walking Sneakers US 6-11New Balance Women's WT510V3 Trail Running Shoes NWTWomens Skechers Go Walk Joy Pivotal Sport Yoga Lightweight Gym Sneakers US 6-11 , Skechers Sport Women's All In Fashion Sneaker - Choose SZ/ColorASICS WOMENS GEL CUMULUS 18 T6C8N RUNNING SHOESPropet XV550 Sneaker - Women's Size 6M, Black/Pink , Saucony Triumph ISO 3 Purple/Blue Running Shoes Women's US 9.5 (G2,6)Women’s Adidas Pure Boost X Element Knit Pink Yellow Running Shoes Size 10.5 , Puma Fierce Bright - White - WomensSkechers Sport Women's Gratis Simply Serene Fashion Sneaker ,
"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."