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.NURTURE - 2-TONE BROWN LEATHER 2-STRAP FLATS - LADIES 8.5M , Zapatos de Mujer Rhinestone Leather Women Flats Brand Shoes Woman Boat ShoesEstyle Japanese KoreanUS 5- 8 Chinese Traditional Red Flats Shoes Costume Bridal , Galo Brown Quilted Square Toe Flats Size 8$105 Women's Size 5 Pink Melissa Maisie II Women PVC Jelly Pointed Toe Flats , Aerosoles Womens Traveler Flat Shoe Black & White Fabric Size 8 M US , New VADO Women"s High Top Trainers Shoes LEATHER Fashion Size 7,5 USA/39 EUROSam Edelman Womens Seana- Pick SZ/Color.Womens Casual Fashion Sport Breathable Outdoor Sneakers Running Shoes Comfy NewNew Fashion Canvas Shoe Women's Shoes Harajuku Wind White Shoes Womens Shoes , Marc Fisher Women's Abree Loafer Flat Black Size 7.5 gnoe , A2 by Aerosoles Women's Sunflower Slide Sandal Black Faux Leather Size 12M , Shape Ups Walking Fitness Toning Shoes Platform Wedge Sneakers Creeper ShoesTretorn Nylite Plus Sneakers - Women's Size 8.5, WhiteNaturalizer Womens Morrison White Fashion Sneaker Size 10 (2E) (23902)Nike Women's T-Lite XI 610232-101 (Wide) Training Shoes White [151N] , Women's NikeFlex Supreme Training Sneaker8.5 Outfall Athletic ShoesSaucony Seeker 2 Woman's Running Shoes Size US 7 (A 4,19)Nike Air Max IVO Women Pink Black Silver Size 7 , Nike Roshe LD-1000 Size 6, 6,5, 8.5 and 9 Steel Blue White Green NEW!!Crocs Women's Busy Day Stretch Skimmer Sneaker, Cerulean Blue, Size 5.0NIKE AIR ZOOM ULTRA WOMEN`S SHOES TRAINING RUNNING SNEAKERS NEW SZ 9.5; , Sneakers and Athletic Nine West Obliviator Light Pink/Silver Synthetic , Asics Gel Nimbus 19 Running Shoes - Women's Size 9.5,Diva Blue/Coral/Aqua Splash , 2015 Womens Nike Zoom Fit Agility QS Johanna JFS NikeLab Sz. 8 White 745242-100 , Skechers Women's Endeavor-Venturer Taupe Fashion Sneaker - Size 7 / 8 , Easy Spirit Zamper Suede Brown Walking Shoes Size 6.5MSkechers 197 BLK Women's OG 92 WALK IT OUT Sneaker #BR , New Sperry Top Sider Womens Seacoast Teal Fashion Shoes Size 5Brooks Pure Flow 6 Light weight Running Shoe, Men's - Size 10.5 B Purple / Gray
"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."