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.Torrid D’orsay Black And Silver Flats Size 12W , SOFT STYLE BY HUSH PUPPIES WOMEN'S DELANEY WINE PATENT "CROCO" FLATS-NWOB - (r1)DE OSU/FARO - Women's Ivory Leather Patent Ballet Flats B-7502 -Euro 40 Size 9.5ara Women's Iris Slipper, Natur Lamfell, 38 M EU (7-7.5 US)Life Stride Shoes Sz 8.5 Ballet Flats Debate Brown Flats Patent Slip Ons 8.5M , Ralph Lauren GaIa Black Patent Leather Loafer Flats Oxford Slip On Shoe Size 6.5Women's Multi Color Kenneth Cole Reaction Slip On Shoes Size 9.5 M , FOOT SMART Slip On Comfort Beige Wedge Shoes - 8WTalbots 6.5 Teal Blue Suede Leather Low heel ballet flats Career Cocktail EUC , circus caley rose shadow shoes 10 m by Sam Edelman new in Box suede flat shoesMiu Miu Brown Suede Embellished Low Heel Moccasin Flats SZ 39.5Women's SAS Shoes Gold Bronze Tan Size 9 S Great condition! , VINTAGE ASICS MATFLEX Women’s High Top Athletic Black Sneakers US 8Brooks Women's Glycerin 15 Running Shoes Size 9 W Wide Width , NEW Rockport M77932 Coralee Canvas Sneakers, Women's Red - Choose Your SizePin Up Couture Women's Monroe 01 SlideSonoma Life + Style Women's Mules Dawna Suede Crocs Faux Fur Lined SZ 7M BlackDansko Women's 40/ 9-9.5 Suede Brown Clog Mule Slip on ShoesWomen’s 7.5 ASICS Gel-Kayano 17 Red Silver Yellow Running Athletic Shoes 7012 , J-41 "Genesis" green and yellow sporty ballet flats. Women's 7.5 MEasy Works Womens Bind Fabric Closed Toe Clogs Blue Size 9.0 3vB0Keds Women's Triple Kick Striped Mesh Sneaker, Light Pink, 9 M USAltra Olympus 2.0 Sneakers Shoes Womens 8 Purple Running Athletic Zero Drop , Nike Free RN 2017 Women's running shoes 880840 400 Multiple sizesWomens Nike Air Max Thea KJCRD Black Spring Leaf running training 718646-005 , Merrell Performance Women’s 8 Canteen Pale Lilac Waterproof Leather Mesh SneakerDC Women's Trase TX SE Skate Shoe, Grey Feather Camo, Model ADJS300080DR. COMFORT BROWN LEATHER MARY JANES DIABETES COMFORT WORK SHOES WOMENS SZ 9.5 MPropet Women's TravelFit Walking Shoe, Lime/Blue, 10 2A US , TEVA Womens Original Universal Sport Grenadine Sandal Trail Shoes US 11 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."