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 Womens Boat Shoes Top Sider Size 7 Espadrille Gray Blue Flower 9267568 , J. Crew Gray Leather Italian Elastic Flats- Size 8.5Mint Fit Narrow Daily Casual Ladies Slip On Only Women Ballet Flats Size 7.5NWOB HALOGEN EMILY METALLIC PERFORATED LEATHER WOMENS 9.5 LOAFERS SHOES $109 NEW , Minnetonka Women’s Classic Fringe Softsole Boot Size 5.5 in TANLifeStride Womens indeed Closed Toe Slide Flats, Stone, Size 8.0 4L3x , Traditional Women Slippers Shoes Indian Handmade Ethnic Jutti US 5 , Women's Sam Edelman Fauna Peach Flats Size 6.5 M , FLY FLOT BLACK LEATHER ASTI LOAFERS: Anti Shock, Anatomic, Size 38, Worn Once , NATURALIZER tan black tribal ethnic suede thongs sandals flats 11 DESTINY Brazil , Nine West Womens Blue Leather Flats 6.5 M , Nine West Saxiphone Pointed Toe Loafer Flats 897, Black Multi, 6 US , Rockport BROWN Croc Embossed Leather Loafers Moccasins Shoes 8.5 M MINT, WORN 1X$185 KENNETH COLE STAR STUDDED Brown Suede Designer Comfort Flats 7.5Women's Shoes Bernie Mev. Catwalk Casual Slip On Flats Black Velvet *New* , A35 Aleaa Ballet Flats 595, Nude, 10 US , Circus Sam Edelman Leni Size 10 Flats Espadrilles Moccasins Black Beach BabeREEBOK size 8.5 womens REFLECTIVE gray & white PT Prime lightweight running shoe , Nike 2004 Dunk Low Women's Size 9.5 White Glacier Blue Yellow SwooshMizuno Wave Rider 20 Running Shoes Black Synthetic Women9Medium (B, M)New Balance 571 V3 XLT Women's Lightweight Running Shoes Athletic Size 10SKECHERS WOMENS GO RUN 600 -REFINE W/CHAR , Womens NIKE STUDIO TRAINER 2 Black Trainers 684897 007Vince Blair 5 Slip On - Women's Size 9M, BlackVANS Old Skool Cup (Leather) Aqua Sea Blue UltraCush Pro MEN'S 8.5 WOMEN'S 10Salomon Womens XA Pro 3D CS Green Athletic Hiking Mountain Running Shoes 9Vans Old Skool Zip (Smooth Leather) Black Women's 5 , New Balance Womens Running Shoes Size 8 (4357)NIKE DUNK LOW WHITE BROWN POWDER BLUE WOMEN'S WMNS SZ 9 -12 317813-121 , Crocs Womens Duet Busy Day 2.0 Satya A-Line Fashion Sneaker Shoe Smoke Size 4 M ,
"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."