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.ElevenParis Black Karl Is My Father Slip On Shoes Flats - Women's Size 6.5Taryn Rose Leather and Fabric Flats Size 6.5Sam Edelman Womens Lynda Bright Multi Flats/Mules Shoe Size 9 M , Arizona Ollie Black Womens Loafers Size 9MCole Haan ZEROGRAND Maroon Snake Ballet Flats Size 9.5B Shoes A3 , Jonak Boots femme taille 39 EU marron -ZARA WOMAN FLAT LEATHER CROSSOVER SANDALS SLIDES MUSTARD YELLOW 35-42 2650/301GENTLE SOULS by KENNETH COLE "Edge Slip"MUSHROOM BROWN Pull On Flat Size 6M ANBAlfani Womens Perrlla Fabric Pointed Toe Slingback Flats , NWT WOMEN'S TOMMY HILFIGER BLUE POLKA DOT CANVAS SLIP ON SNEAKER SHOES SIZE 2Children's Reebok Trainers - Winning Stride II , Woollen Slippers, shoes, boots, ALPACA NATURAL WOOL 100% GOOD GIFT!!! ALPACA SEAbeo Aero Sneakers Shoes Cori Champagne Womens 11 M Silver , Ahnu Gray Blue Mesh Buckle Strap Athletic Trail Hiking Walking Shoes Women's 6.5 , Women's K Swiss X Lite ST CMF Charcoal/Pink 93523-044 Brand New!!! Memory Foam!!BROOKS Womens Size 9 M Ravenna 5 Running Shoes Sneakers Purple Pink Pre-ownedMerrell women's size 6 sneakers running shoes walking trail VibramVLADO Women's 'ATLAS II' Gray / Fuchsia SHOES - 9 Cute Pink , Nike Dual Fusion ST 2 Womens Running Shoes Size 6M Blue Waffle Sole- , Women's Asics GT 2000 V 4 Running Shoes 9.5 Turquoise Green Blue Hot Pink T656N , Nike Free 5.0 Sz 7.5 Women Pink Neon Running Shoes EUC YGI M6-78 , New Nike Womens Free 5.0 V4 Ns Pt pureplatinum/white/white Running Shoes Size , Nike Zoom Winflo Women’s Black/Hyper Punch Running Shoes Size 8 EUC , Women's Ellie Women's Payton-V For Your Selection Athletic ShoesWomen's Franco Sarto Women's Brewer Flat Large Assortment FlatsNEW VANS AUTHENTIC LO PRO CITY BLACK TRUE WHITE SHOES WOMENS 6.5 MENS 5 VAULT , NIKE AIR ZOOM ULTRA WOMEN'S TENNIS SHOES - WOMEN'S SIZE 8 , ADIDAS Distancestar Blue White Pink Camo Track Field Shoe Spikes NEW Women 8.5 9 , Women's NIke Zoom Fit Sneakers, New Black White Mesh Sport Running Shoes Sz 12Reebok Ziglite Running Shoes Avon Breast Cancer Crusade Women's 8 Gray Pink ,
"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."