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 Bendables Womens Slip On Bicycle Toe Loafers Sz 8 M Brown Leather Comfort , Shoes Of Prey Peep Toe Flats SZ 9 - 39 , Cole Haan Black Women’s Ballet Flats Size 5, NWBC. Wonder Ballet Flats Blue Velvet Women's 8.5 M Jeweled Blue/Gold Bow at Toe A1**Anne Klein Noris Loafer - Women's Size 7.5 M, Black , Calvin Klein Evalyn Red Womens Shoes Size 7 M Flats MSRP $119 , Naot Matai Leather & Brown/Bronze Suede Mary Jane Comfort Shoe SZ US 8-8.5Bernie Mev Women's Lulia Wedge Pump Sandal, Black, Size 37 EUEasy Spirit Women's Danleys Size 6.5 M Loafer Burgundy Stretch Fabric Upper NEW! , Avia 9997 Avi Motion Archrocker Flex OrthoLite Brown Walking Sneakers Shoes Sz 8nike womens free 5.0 TR FIT 4 PRT running trainers 629832 006 sneaker , Women's Drew Rose Black Diabetic Walking Shoes Mary Jane Size 9 M , Clarks Leather Perforated Flats Medora Nina Black 10M NEW A287335 , Rocket Dog Campo Sneakers-Women's size 8 M Grey , DESTOCKAGE MULES @ PANTOUFLE MAISON DE L’ESPADRILLE 43 LA CAGE AUX FOLLES , Women casual shoes 2017 New Arrivals fashion Breathable mesh women shoesBrooks GTS 16 Women's Running Shoes Size US 9 B Silver , Nike Womens Size 9 () Prestige Orange Yellow White (2008) 318972-781 , NEW $69 Womens Skechers Performance Go Walk 3 shoes, size 10 black/grey , Brooks Ravenna 7 Women's Running Shoes Size US 12 Med (B) Blue , Saucony Womens Cohesion 8 Size 8.5 G466 , NEW REEBOK WOMENS CLUB C 85 , New Balance Women's Classics WRL420 Slip-On Sneaker Size 6 NIB , Skechers Womens Next Step Running ShoeECCO Womens Sz 40 Hiking Walking Sneakers Shoes Brown Leather (S2)Baskets Femme samples shoes ETNIES DROP-OUT BLACK GLAM WOMEN , Excellent ASICS GEL-CUMULUS 18 2016 Womens 10, 42 EUR Blue Red $120 , New Balance 1540v1 Womens Walking Health Shoes Size 12 2A Narrow White Purple , Fila Womens Memory Workshift Cross Training ShoesSteve Madden Ellias Side Zip Fashion Sneakers 909, Black, 6.5 US ,
"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."