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.Danny! City Classified Women's Knot D'orsay Slide In Ballet Flats in Beige Linen , Black Silver Spikes On Ballet Flats Round Toe Sexy Shoes Size 5 , PALLADIUM Leather Ballet Flats Womens 5.5 US 36.5 EU Brown Slip On Casual Shoes , Circus by Sam Edelman Leni8 Espadrille Slip On Flats 712, Rose White, 10 US / 40Dr Scholls Women's Equalchop,Willow Size 9 , Steven By Steve Madden Pappy Platform White Sneaker Size 8CLARKS Womens everlay kennon Closed Toe Thong Slide, Brown Leather, Size 6.0 , Sperry Top-Sider Leather Boat Shoe Womens Brown B-14 Size US 7M Pre OwnedWomens 7.5 M Born Chesire acciaio textured metallic pewter blk ballet flat shoes , Women's Asics Size 9.5 Running Shoes Gel Foundation 5 Sky BlueDAWGS Mens Chestnut Microfibre Scuff Slip On Size 8-9 USNew Women's 88 DALE EARNHARDT JR. size 5 REVO SHOES SNEAKERS RACING NASCAR , Converse Chuck Taylor All Star Low Top Canvas Sneakers Women's Sz 9 (152809F ) , Lewit Pink Velvet platform Arlo Slip On Sneaker (size 8 US, 38 EU)Nike Wmns Free Rn 2017 Run Cargo Khaki Neutral Olive Running Shoes 880840-301 , NEW BALANCE WOMEN'S CUSH HEEL PILLOW YELLOW SNEAKERS WX711 NEW WITHOUT BOXSkechers Shape Ups Woman's XF Accelerators Fashion Sneaker Blue/Silver Size 8.5 , Women Light Casual Athletic Sports US Shoe Size Sneakers Walking Slip On Navyadidas Womens Mana Bounce Purple Running Shoes Fitness Gym TrainersAdidas Adipure Sport Athletic Shoes - Women's Size 8, White/Sky Blue , Vibram V-Run Shoes - Women's size 7/7.5 - Neon Pink/LimeVans Women Authentic - Iridescent Eyelets pink wild rose VN03B9IEUADIDAS CRAZYTRAIN CF W BLUE WHITE BB1516 ATHLETIC TRAINING WOMEN'S SIZE 6.5 NWOB , Skechers 48855 LITE STEP Slip On Shoe - Women's Size 9 - Gray , PUMA Women's Basket Platform Core Fashion Sneaker Puma Black/Gold Size 9ASICS Women's Gel-Lyte Komachi Low Top Sneaker Glacier Grey/White Size 7 , Women's Girl's Running Training Sneakers Reebok SoQuick Sports Trainers ShoesSimple Womens Satire Canvas Casual Low Fashion Sneakers Charcoal Sz 6 -10 WIDE , Saucony Women's Endorphin 2 Track and Field Shoe - Choose SZ/Color , Adidas PureBoost X Women's Running Shoes Sz.10 US Grey NWOB ,
"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."