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.Born Womens Black Leather Mary Jane Shoes 7.5 , PINK & PEPPER Womens QUEENIE Black Multi Clogs Size US 8M (8888448-447713)Dark Pink Leather WHITE MOUNTAIN PotLuck Woven Top Loafers 7 M , What's What by Aerosoles Olive Green Suede Loafers - Women's Slip On Shoes - 6M , JOAN & DAVID - BURGUNDY PATENT LEATHER FLATS - LADIES 7.5MPatagonia Gilia low tide Women's Green Slip on Shoes Sz USA 10/(#Lot2 , Kalso Earth Shoe Pace Forest Women's 5.5 B Green Oxford Casual ShoesWomen's Privo by Clarks Size 7M Ballet Flats Loafers Shoes Size 7M Black D8Women's Bass Romana Loafers Shoes Flats Size 7M Black Leather Bow Career G2 , B.O.C. Born Concept Women's Shoes Sz 7/38 Black Leather Slip-On Loafers ComfortNIB - Corkys Float Womens Slip On Sandal in Denim Sizes 6-10Use-Custom-Brand Womens jess Low Top Slip On Fashion Sneakers, Black, Size 7.0 U , CONVERSE JACK PURCELL All Star Chuck Taylor CTAS Blue Spruce women's 7.5 / men 6Women's Skechers You Unique - Grey/Blue - Width: med - WalkingWomen's adidas stan smith Op Have Long Enjoyed Great Fame Athletic ShoesNew Balance US 574 Genuine Suede Made In USA Sz 5.5 Female 22.5 cm , Keds Women's Glimmer Canvas Fashion Sneaker - Choose SZ/Color , ASICS WomenS Gel-Solution Speed 3 Clay Tennis Shoe- Pick SZ/Color. , Amazing Black Labrador Print Slip Ons For Women-Express Shipping , Asics Gel-Pursue 2 women's running shoes trainersNew CONVERSE CT UPTOWN MID Pink Canvas Trainers 143957F , Baskets Femme DC SHOES STUDIO SD MaroonNew FLY LONDON 'Maco' Women's Black Nubuck Low-Top Sneakers Size 10-10.5/41Fila Womens Memory tempera-W Running Shoe- Select SZ/Color.Womens ASICS GT-2000 3 T550N Running Training Athletic Shoes Gray Pink Size 6.5 , NEW! New Balance Women's Fresh Foam Cruz Running Shoes Coral #wcruzoc 106O pz , Roxy Womens Lido III Shoe Flat- Pick SZ/Color.Report Women's Aysun Fashion Sneaker - Choose SZ/Color , Hibou Womens Payne's Gray Casual Chelsea Slip On Leather Boots Left 7 Right 8REEBOK WOMENS YOURFLEX TRAINETTE 7.0 LMT TRAINING SHOES SIZE 9 ,
"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."