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.Pierre Dumas Womens Shoes NEW $40 Moni-29 Black Patent Ballet Flat 6 M , DESIRE BROWN LARDS65 Women's Shoes Size 7 () Leather Mary Janes MephistoLadies Spot on pink canvas slip on shoes F2233Sonoma Women's Leather Flat Sandals Color Dark Olive Green Size 8.5 M NWOBRocket Dog Women's Colt Joshua Fabric Ballet Flat, Charcoal, 6.5 M US , Fila Alumni Black Slip On Flat Moccasin Shoes (Womens US 7.5) 5SC10132-018 GR , Womens MERRELL 'Apure Saddle' Brown Leather Loafers Flats Shoes SIZE 9Peron Vintage Croc Embossed Leather Loafers Shoes Women's Size /US 8 , womens sofft brown leather loafers shoes size 8 1/2Cole Haan Leather Pinch Loafer Women's 9 , Cole Haan Amalia Skimmer Charcoal Multi Haircalf Women's Slip On Flats Size 9 MKEEN Cream Leather Mule Walking Slip On Shoes Womens 8Seychelles Women's So Nice Fashion Sneaker , Eastland Womens crystal Closed Toe Mules, Wheat, Size 9.5 eLDt , Array Size 6 Wide FRESCO Black Leather Slip On Loafer New Womens Shoes , US Polo Assn Sneaker Shoe Black & White Size 7 UnisexMerrell Womens Pace Glove Lavender Lustre Water Resistant Walking Shoes Sz 6Women's 9 M Jena Espadrille Sneakers - Universal Thread Gray Star CutoutsSkechers Shape Ups Womens Mary Jane Toning Shoes Sz 8.5 Black -5432 , NEw Balance Women's 855 White/Blue Supportive Walking Shoes Size 8.5 , New Balance 574 Sport Running Sneakers Pink / Turquoise Girls Women's Shoes 5 , Nike Roshe One Womens Running Shoes Size 8 , Womens Brooks Adrenaline GTS 14 Running Walking Training Shoes, Size 7.5M , Women's Yellow Box Women's Everly Sandal To Adopt Athletic Shoes , Nike Black White Basketball Shoes Womens Sz 10 Hyperdunk High Tops Air CushionWomen's Converse Patbo Chuck Taylor Hi 554867C Size 5~9New Nike Women's Air Max Invigor Running Shoes Cool Grey 917544-001 SZ 6.5 , Nike Revolution 2 Women's Running Shoe 554900 034 Size 8.5New Balance 928 v2 Black Athletic Walking Sneakers Women's US 7D WW928BK2 , Skechers Sport Womens Breathe Easy Symphony Fashion Sneaker- Select SZ/Color.
"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."