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.IKRUSH Womens Fifi Chunky Arched Leopard Sport TrainerBorn W3655 Buckle Moc Toe Stitched Pebbled Leather Clogs Mules Women's US 62020 New Arrival Women Flat Shoes Oxford Shoes Genuine Leather Shoes , L L Bean Women Tan Leather Boat Shoe Mule Low Back Tassel size 9.5 M Clog ShoeJOSEF SEIBEL (The European Comfort Shoe) BURGUNDY SZ 37.5 38 EURO FLATS/SANDALMerrell Jungle Moc gunsmoke women's size 6.5 suede loafers comfort trail hikingAJ VALENCI size 7.5 M mulesMunro American Cindi Women 9 N Shoes Slip-on Stretch Fabric Black BE3A718 , Old Beijing Cloth Shoes Rubber Sole Flat white , Andre Assous New Marsha Multi-Color Womens Shoes Size 9 M Flats MSRP $159 , women's shoes OLGA RUBINI 9 () moccasins slip on blue paillettes BX787-39Klogs Landry Womens Clog Display Model Shoes Caramel 6 MWomens 8.5 B BRONZE LEATHER Aravon Faith Brown Slip On Loafers Shoes New BalanceEric Michael Womens Shoes NEW $145 Omar Black Taupe Suede Slip On Platform 35 52018 Fashion Women's Sneakers Sport Breathable Casual Running Outdoors Shoes A2Asics Gel Cummulus 14 Womens Size 6.5 , SOLE SOCIETY WOMEN'S "KALIN" CHAMBRAY SNEAKERS -NWOB- NEW SHOES! LIGHTWEIGHTDr. Scholl's Womens Madison Low Top Slip On Fashion Sneakers, Silver, Size 8.0 xAsics Gel-Landreth 3 Running Fitness CrossFit Jogging Shoes Women Size 7.5Thom McAn Men's Parker 35341 Slipper Slip-On Shoes Brown / BlackNIKE REVOLUTION 3 SNEAKERS 819303-002 Gray White Peach Training Running 7.5 , Saucony Guide 10 Running Shoes - Womens Grey Teal Running Shoes Size 8 (16627) , SANUK RUNAROUND CHARCOAL SLIP ON VEGAN SANDAL US 9 / / NWTWomen's GEOX Shoes 380703 GreyｘMulticolor 36 Fast Shipping Athletic ShoesWomen's Converse Rose Gold Size 6 2017 New Athletic ShoesWomen's Steven Madden Black Studded Flats Quality Superior Flats , Nike WMNS Lunar Sculpt womens train training shoes NEW voltage green black volt , ASICS Women's Gel-Contend 4 Running Shoe Diva Blue/Silver/Orchid Size 8M , NIKE Womens Solay Thong Print 882696-602 ARCTIC PINK/WHITE Womens Size 5 , Puma Carson 2 Molded Women's Running Shoes Black/White 190036 03 Sz6-10 K
"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."