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.Dansko Professional Nursing work Clogs Womens Sz.8 US / 39 Euro , Bare Traps Womens Black Leather Mary Jane Wedge Mule Shoe - Size 9M , Vintage Ellen Tracy White Leather Shoe With Tassels SZ: 8.5 N , Women's Bandolino Sneakers sz 6.5m black suede slip-on shoes EUC , Born T-Strap Flats Size 7.5 Dark Brown Slip On Comfort Shoes Retro DetailANNE KLEIN SPORT BUTTONS BALLET FLAT WOMEN'S NATURAL/BLACK US 6M NEW WITHOUT BOX , American Eagle Flats Womens Size 8M Houndstooth Gray Jewel Front Bow-3673 , Clarks Womans Shoes size 8.5 BlackShellys London Womens Abeniel Canvas Round Toe Loafers Gray Size 6.0 7Upa , Clarks Somerset Black Suede 9.5 Slip On Shoes Loafers , les p'tites bombes basket 4-ANEMONE V.Noir P38 neuves Aut/Hiv 2018/2019 , Clarks Daelyn Hill Burgundy Red Nubuck Leather Slip On Shoes 7W NEWZARA NEW WOMAN MID-HEEL BALLERINAS BOW RED 35-42 REF.7532/301Pastry All High Top Fashion Sneakers Shoes Size US7 UK52018 Fashion Womens Running Shoes Sports Sneakers Athletic Breathable Outdoors , Qupid Womens Narnia Gray Toe Cap Fashion Sneakers Shoes 6 Medium (B,M) BHFO 4369Womens High Top Hidden Heels Round Toe Sneakers Trainers Mixed Colors Shoes , NIKE AIR VISI PRO IV Women SHOES SIZE 10 BRAND NEW 587562 016 , New Balance "310" black and purple running shoes Women's 10 B (eur 41.5)Skechers Shape Ups SN 12320 Womens Sz 10 US Toning Comfort Walking ShoesNike WMNS Classic Cortez Leather women lifestyle sneakers NEW white 807471-101 , Asics Gel Lyte III 3 Sneakers Shoes Women Sz 6.5 White NEW $110ASICS LIFT MASTER LITE WOMENS CROSS TRAINER SHOES S659Y NEW SIZE 9Saucony Jazz Original Athletic Women's ShoesAdidas Adi Ease W Shoes (White/Tan)Geox Women's Nihal 5 Sneaker - Choose SZ/ColorAsics GT 2000 v 4 Women's Running Shoes Size US 10.5 M Midnight Blue T656N , Salewa Hiking Sneakers Shoes Womens 7 WS Wild Fire Black Mountain Trainer , Brooks Ariel '16 Running Shoes, Women's Size 8 D, Teal/CharcoalPuma Vikky Platform jr Blue Walking Shoes 5.5 (7 Women ) ,
"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."