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.Sperry Top Sider Womens Luna Eyelet Ballet Flat Size 6.5M White LeatherBass Loves Rachel Antonoff ZOE Tan Floral Oxford Shoe Women 9.5M canvasLANE BRYANT Women's BLACK Slip-On Shoes SZ 7W NEW , GENTLE SOULS Women 7 PENN Cork Ballet Flats Loafer $195 NWOB Studs Tan Brown , Clarks Janey Mae Oxfords - Women's size 5.5 M BeeswaxWomen's Shoes Calvin Klein MONET MATTE SNAKE Loafer Embossed Leather BlackSteve Madden Women's Genette-P, Blush Satin, SZ 6.0 M NEW DISPLAY DEFECTS D7973 , SNAPPY-1-05 WOMEN GLITTERATI SNEAKER CAPE ROBBIN BLACK , Womens rhinestone square toe slip on flat heels fashion casual shoes hot a592Womens Chinese Retro Hidden Wedge Heels Slip On Loafers embroidered Dance Soes , Comfortiva Womens grace Closed Toe Slide Flats Black Size 7.5 n7OO , **Skechers Go Walk 4 Pursuit Casual Slip On Shoes - Women's Size 9.5 - BlackPUMA WOMENS CABANA RACER BLACK & WHITE RUNNING SNEAKERS SHOES SIZE 7 PREOWNEDRockport RocSports Pro Walkers Womens 7.5M Tan Leather M7102 Walking Shoes VGC! , Nike free 5.0 running shoes size 8 US black w/pink swooshNike Initiator Women Size 10 Gray Runners , Puma Womens Vikky Mid Black High Top Sneakers Shoes 5.5 Medium (B,M) BHFO 6664 , Nike Shox, Women's Size 10. Pink And White shoesJessica Simpson Womens Fusto Low Top Slip On Fashion Black Heather Size 7.5 lN , MIZUNO WAVE INSPIRE 8 RUNNING SHOES / MULTI COLOR ( SIZE 8 ) WOMEN’S , Women's women skechers shoes Good Design Athletic ShoesNike Women's Nike Flex Trainer 4 Shoes, 643083 603 Sizes 6.5-12 Fchs Frc/Wht/HypSteve Madden Women's Gisela Fashion Sneaker - Choose SZ/ColorWomen Athletic Sneakers New Balance Running Shoes Mesh Suede Upper Gray WL420CRDNEW Puma CRETE PIQUE Women's Shoes Size US 7 , Asics Gel-Fit Yui Athletic Shoes - Women's Size 9.5, Black/Silver/White , New Balance 1080v5 Womens Running Training Shoes Size 7.5 Gray Blue Purple , Asics Women’s Pink Black Gel Quantum 360 Size 8.5Avia Women's 344 Slip Resistant Ankle-High Training ShoesWomens NIKE Prestige IV High 614288 001 11 US 8.5 EUR Shoes
"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."