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.WOMENS 7 M EASTLAND BROWN LEATHER MOCCASIN FLOWER MULE SLIDE FLATS SHOES , CLARKS Springers slip on loafer shoes womens size 6 tan leather 1 inch heel , Womens Clarks Bendables Leather Slip On Loafers Shoes 7.5 WBlue nn Glitter Sexy Point Toe Comfortable Slip On Women Flats Shoes Size 6.5 , Report Whiskey Brown Gold Plate Pointed Toe Comfort Ballet Flats Size 7Ankle Strap Snake Skin Flats Fashion Ballerinas Brown Tan PU Women's Shoes NewSAS BLACK SHOES WOMEN'S SIZE 9 1/2 M , BOC Born Concepts Peggy Clogs Black Embossed Leather Comfort Shoes Size 8.5MNaturalizer Brown Leather "Parama" Sneaker Size 7M , NEW Circus By Sam Edelman Womens 8 Rose All Day Flat Espadrilles Pink Closed ToeJ. Crew Silver Metallic Pom Pom Slip On Womens Flats Size 9 , LIFESTRIDE Womens LOCK Pewter Stingo Mary Jane Flats Size US 9N (C8212S1900)Crocs Pink Slip On Rubber Mules Size Mens 8 Womens 10 , Betsey Johnson Size 7.5 Sandals Slingback Flats Beige Tan Floral Open Toe RoseWomen's Canvas Sneakers With Elvis Portraits "Burning Love" NWOB Size 9 , NEW Ivanka Trump Zessios Blue Leather Slippers size 10 Flats Loafers Shoes , Women's Asics Gel-Kayano 21 White Hot Pink Emerald Running Shoes T4H7N Size 8SoftWalk Women's Naperville Ballet Flat, Black/Black, Size 7.0 TYBUWomens Adidas Stella McCartney Ultra Pink Pure White Boost Running Trainers 10.5Reebok Womens Classics Melody Ehsani Freestyle HI INT Hidden Wedge Grey 6-10 , HW2 New Hoka Vanquish 2 Running Street Road Pavement Shoes Women 7 Purple & Red , Nike Womens Free RN Running Shoes Trainers Sneakers Pink 5 UKNew Womens Columbia "Peakfreak Xcrsn Xcel" Omni-Grip Hiking Walking Trail Shoes , New Balance Womens Wx608v4b Black Cross Training Shoes Size 9 (C,D,W) (366259) , Skechers Women's Goldie Glitchy SneakerUSED Lacoste Women's Shoes 4 Black , Vibram Fivefingers Athletic Shoes Women’s US 7- 7.5 Excellent ConditionBrooks Women's Transcend 2 Carribean/Poppy/White Running Shoe 6.5MSkechers Women's On The Go City 3.0 Immerse Charcoal 14759/CHAR , Palladium Sibay Print Women's 93667-644-M Old Rose Sz 7 1/2 US ,
"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."