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.Ecco Shade Casual Bicycle Toe Brown Oxford Shoe Women's Size 39 ( US 8 - 8.5 )Navy Round Toe Causal Silp On Faux Suede Strap Buckle Padded Womens FlatsCANNON RIVER BLUES WOMAN'S SHOES SIZE 10 SLIP ON CLOG STYLE BLACKSAS FreeTime Sage Tan Oxford Tripad Comfort Walking Shoes Women's Size 9WClarks Women's Size 7 M Flats Leather Shoes Slip Ons White Brown DetailsWomen's Ariat Comfort Casual Slip-on Shoes Slides Brown Leather-Side Buckle-9.5B , Frye Anna Harness Ring Ballet Flats Brown Bronze Studded 7.5 M 72150 LeatherDANSKO Hilde Women's Size US 9.5 / 10 Mary Janes Silver Gray Loafers �b2 , New Balance Womens White Walking, Hiking, Trail Shoes Size 7.5 (C,D,W) (261551) , Nycole St. Louis Brown & Beige Off White Womens Golf Shoes 7-M Quebec CanadaNice! ECCO BIOM TRAIL ARGON DARK SHADOW WOMEN'S TRAINING SHOES 9 - 9.5 (40)Skechers SN22467 Relaxed Fit Memory Foam Slip On Flat US Shoes Size US 6Womens Mesh Bling Glitter Breathable Sneaker SLip On Athletic Sports Shoes VogueSaucony SZ 8M Cohesion 8.5 Women's Running Shoes Gray S15218-12 Free ShippingCalvin Klein Juno Women's Velvet Low Top Leather Trim Platform ShoesWomen's Ladies Reebok Alperez Classic Trainer Shoes, Trainers, Sneakers - Purple , $179.99 Puma x Solange Women Trinomic XT2 Plus Swirls (blue / sulphur spring / b , Womens Vintage Straw STEVE MADDEN Wedge Platform Flip Flops Sandals Shoes Sz 7 , Skechers Go Walk 4 Noble Athletic Shoes - Men's Size 11.5, Black/GreyWomen's Easy Spirit Hugs4 - White - Width: med - WalkingPUMA FIERCE evoKNIT Women Sneakers (7.5 M, PEACOAT/WHITE)Vans SK8 HI ZIP CALIFORNIA Italian Weave/Pig Suede Women's Shoes 6Steve Madden ECNTRCQT Quilted Sneakers Slip-On Casual Shoes Women Blush Size 7.5 , Brooks Glycerin 14 Womens Running Shoe Sneaker Charcoal Grey/Pink SIZE 9VANS Sk8 Hi (Pig Suede/Fleece) Black/Blanc de Blanc Skate Shoes WOMEN'S 8Womens Nike Lunar Skyelux Grey Green Size 6 NEW , Jeffrey Campbell Boulevard Block Flat Shoes Ivory Grey Size 6 New , New Balance Women's Ww496sl3 Grey/Pink Running Shoes SZ 8.0 M D2860 , Softwalk Simba Slip On Lightweight Comfort Loafer Charcoal Gray Womens Size 8NIB Women's Nike Flex Trainer 4 Shoes Lunar 643083 005 Supreme Dart ,
"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."