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.Clarks Canvas Tan/Brown Mules slip-on Women’s 7M , Women's FERGIE ASTER Black/Gray Print Bow Fashion Casual Slip On Dress Shoes Sz6 , Butterfly Twists Olivia Tan Leopard Womens Ballerinas Flats Shoes , Lands End Womens Brown Leather Clog Sz 7B , DONALD J. PLINER MADE IN SPAIN SLIP ON SUEDE LEATHER SHOES SIZE 8M BROWN , Cole Haan Ballet Flats Suede 7.5 B Women Tan Brown G Series , Donald Pliner Vevi Beaded Aztec Slip On Loafers Italy 8 MVINCE CAMUTO CANITIA WOMENS GRAY LEATHER STUD STAR SLIP ON TENNIS SHOES 7 NEW$80 NAUGHTY MONKEY Stop The Madness Flats ~ Blue / Brown Leopard ~ NEW Size 6EARTHIES BY EARTH ESSEN Animal Print Ghillie Ballet Flats Size 5.5ED Ellen Degeneres Daire Sneakers Womens 7.5 Black Slip on Shoes LoveAmalfi by Rangoni Women's Emiro Flat, Black, 6.5 M US , ***NEW***Authentic Bensimon Tennis CanvasSize 6 U.S. 37 Euro New , FILA 2017 Hiking Trail Running Sneaker Women US 8 Leather SyntheticWomen's Skechers Shape-ups Walking Shoes Size 10 Brown Leather Mary JanesSam Edelman 7 M Taupe Grey Patent Leather Loafer Shoes Designer Wear To WorkKeen Womens Ambler Gargoyle/ Allure Gray Hiking Shoes US 6 , LADIES BLACK METALIC SPOT ON LED LIGHT UP SOLE TRAINERS F80189CONVERSE CHUCK TAYLOR DAMAGED HI CT BLACK RASPBERRY SCRIBBLES SZ 4-12 * 108855FWOMEN'S CHAMPION GUSTO NEON PINK GRAY LEOPARD PRINT RUNNING SHOES-SIZE 5 1/2 , Asics Gel Kayano 19 Womens Pink Black Neon Yellow Running Shoes Size 8.5 , Skechers Equalizer Cross Training/Running Shoes Women's Size 8.5 11890 CCLB EUC , Women's KALINYA PEPI WOMENS/LADIES SHOES/SANDALS/FLATS/COMFORT/LIGHTWEIGHT/ON SALE! Inexpensive SandalsNIB Adidas Women ZX Flux W B35310 Shoes Choose Size Bk/RdNew J.Crew SeaVees Blue White Legend Canvas Sneakers In Gingham Check Print 8 , ASICS Womens Gel-Foundation Gray Pink Running Workout Shoes Size US 6.5 T5H5N , Women's Adidas Black, Purple, and White "Adizero" Running Shoes Size 10 , ASICS Womens - Green Running Shoes Size 8.5 (367671) , Women's Comfortable Platform Walking Sneakers Casual Tennis Air Fitness ShoesCoolway Freestyle Treck Ace Slip On Sneakers, Women's Size 6 NEW ,
"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."