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 $42 Tara Bronze Ballet Flat 6.5 M , Bearpaw Womens haven Suede Closed Toe Oxfords, Slate Blue, Size 6.0John Lewis Leather Sandals Shoes Size 5 Size 8 Au Very Good ConditionHUSH PUPPY SHOE SOFT STYLE LADIES SIZE 7M BROWN SLIDE-ON SHOE FLAT LOAFERSam EDELMAN - BEIGE Perforated Ballet flats cushioned sole US size 8-1/2M - GUCNEW Womens SPERRY Duckling Navy Blue STS93574 Low Rain Boots ShoesPureSole Black Leather Barlet Slip On Clog Shoe 8 NEWSperry Top Sider Angelfish Women's Slip On Boat Shoes 9102898 , LES P'TITES BOMBES : ballerines modèle ADISON - collection hiver 2014-2015Pointed Toe Loafer Genuine Lamb Leather handmade Ladies BLACK 38 (7) , EASY SPIRIT 5003 512 000 WOMEN'S MOTION SHELL LEATHER SHOES SIZE 6B NEW IN BOX , WOMENS NEW BALANCE 677 CARDIO COMFORT LIGHTWEIGHT SHOES Sz 9.5 , New Balance WW1442 Rock&Tone women's walking shoes, gray/Blue US size 8 mediumNew Balance Womens 560 Running Shoes Size 8 1/2 White Gray Pink SUPER NICE , Saucony Women's 7.5 Grid Fusion 3 White NEON Blue Running Shoes 15063-10 ~16Asics Gel-Rocket Women's Volleyball Shoes B455N White Silver Size 13 NWOB! , Women's SKECHERS Flex Soles Memory Foam Heather Gray Jersey Sneakers SZ 7New Nike Womens Internationist shoes sneakers 872922-001 Sz 7 Black Denim , Women's totes Women's Ruby Black ngenious And Practical Athletic ShoesNew Nike Womens Unreleased Shoes 882263-001 sz 7 Black-white. RARE FREE SHIPPINGNike Free TR Flyknit 3 Women's Training Shoes, Size 13, 942887 100Vibram FiveFingers Alitza Women's - 37 US 5.5-6Nike Womens Zoom Elite+ Size 11.5 Pure Purple Grey Volt Running Shoes 487973 517 , Brooks Ariel 16 Women's Shoe Anthracite/Purple/Grey - size 7.5 MNew Women's Skechers 11959 D'Lites Looking Glass Walking Shoes Size 6.5 (N21)New Balance Fresh Foam Cruz v1 Sneakers-Women's sz 7 B BlackMerrell "Chameleon Arc Stretch" Hiking Shoes Women's Size 7 (r)NIB NIKE CORTEZ Women Youth SIZE 7 Black Vivid Pink White Sneakers , Ahnu Sugarpine Sneaker - Women's Size 8 Green , Ahnu Women's Taraval Black Leather Athletic Walking Shoe Porter Size US 7.5
"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."