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.Womens SOFFT Size 6 Black Cecille Flats Shoes Leather Penny LoafersCROCS 'Espdrillaslponw' Myel/gld Ladies Canvas Shoes UK Sizes 3 & 9 (MG) , ETIENNE AIGNER VINTAGE Womens "Arlington" Brown Loafers w/ Gold CLASP SIZE 7crocs Womens Kadee Animal Print Flat- Pick SZ/Color.CLARKS MULES BROWN LEATHER REPTILE ACCENT MONK STRAP WOMEN SIZE SIZE 7 W , NIB Ladies Frye Melanie Perforated Slip On Leather Shoes Pewter 8M $158 NEWBadgley Mischka Bianca Flats, Women's Size 8, Ivory Satin , Fila Hyper Split 4 Women's Pink/Black/White Athletic Shoes 8M , Airspeed High Top Sneakers Womens Size 5 Galaxy Cosmic Print Silver Glitter Toes , ASICS Womens Gel-Kayano 22 Running Shoes Athletic Size 9.5 Blue Pink Purple , new Spring summer Korean fashion leisure Breathable mesh Sports shoes , Clarks Azella Theoni Slip-on Loafers, Navy, 9.5 US / 41 EUNEW BALANCE 857 TRAINING ROLLER BALL SHOES - SIZE 8.5 WIDE 4E WOMEN , Propet Womens Eden Strap Ivory Walking Shoes Size 7.5 (20100) , Skechers Women's Memory Foam Microburst Imagination Slip On Navy 23326/NVYNew Women's New Balance Silent Hunter MD 500 V4 - Spikes included - Size 6.5 , MINNETONKA Kilty Hardsole Women | StoneSkechers Women's Bright Idea -Good Start,Sneakers GRY Gray Med. Slip-On , NEW ASICS GEL LYTE III WOMEN'S RUNNING SHOES ICE BLUE /ICE BLUE 100% AUTHENTICFitFlop Grey Uberknit Crystal Slip on Comfort Sneaker 8.5 40 Sale , WMNS AIR FORCE 1 '07 315115-171 WHITE/ MET GOLD DEAD STOCK & YELLOWING SZ:72016 WMNS Nike Air Force 1 Hi Premium QS SZ 10 Bleached Lilac White 654440-500KEDS WF54943 - TRIPLE DECKER FRUITY ANIMALS Size: - Color:Brooks Womens Variation Black Walking Shoes Size 10.5 (25373) , Chicken Canvas Shoes, High Low, Women Men, Cute Bird Lover Gift, Hen Rooster PetLE COQ SPORTIF Saint Malo W Women's Shoes *All SizesPuma Carson Runner Womens Running Sneakers Black and White Choose Your Size , New Asics Women's Metro Walk SL Casual Walking Shoes - Black/Onyx/Mint - 7.5 , Altra Zero Drop Olympus 2 In Charcoal/ Peacock Womens 8.5 Nice! Running Shoes , Women's Pink/Black Nike Zoom Structure 18 Athletic Running Shoes Size 10
"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."