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.Ladies Keds Canvas Shoes Label Rookie LcelssOld Navy Womans Flats Size 9 Beige Bow Scrunch BalletCrocs Women's Cobbler Fuzz Clog Size US 7 Excellent Condition!Crocs Mammoth Women's Flat Black Ballet Flats Size 10 Fur Lined EEUC , SAS Genuine Handsewn Leather Tassle Comfort Shoes Beige Sz 11 , Vince Maxwell 2 Yellow Womens Shoes Size 8 M Flats MSRP $225 , Sam Edelman Frederick Flats 6.5 Women’s Black Leather Crisscross Ballet Flats , Nine West Womens Anastagia Pointed Toe Ballet Flats, Red, Size 5.0 DNlQ , Woollen Slippers, WOMEN'S, MEN'S, boots, mules WOOL GOOD GIFT!!! GORALESkechers Women's Ez Flex 3.0 - Swift Motion Slip-On ShoeWomens Nike Prestige 3 Skinny High Athletic Shoes 551649-564 Size 10 , Brooks Ariel 14 Womens Pink/Silver Running Shoes Size 8Womens Nike Lunarglide 6 Running 654434-001 Black/Gray tennis shoes sz 11Women's Sperry shoes 7.5 For Your Selection Flats , NEW! Nike Womens Zoom All Out Flyknit Running Trainers 845361 300 Size: US 6Skechers Sport Women's Microburst One up Fashion SneakerBlack9 M US , Women's Skechers Bright Idea - Pasha 23600/GRY Shoes NIB , NIKE LUNAR CONTROL VAPOR GOLF BLACK SIZE 8.5 NEW RETAIL $175 (849979-001)New Balance Women's 711v3 Cross Trainer White 8 W US , Asics Running Shoes T580N Women’s 11RARE VINTAGE JORDACHE LEATHER HIGH TOP SNEAKERS SIZE 10 WHITE & PURPLENike Flex Running Shoes Sneakers Pink Neon Green Accents Women’s 7.5 Retail $80 , Women's Saucony Grid Hybrid 3 Running Shoes Black Size 9 123B , ONITSUKA TIGER - L. ULTIMATE 81 (HN567-1390) - SIZE 7 - 50% OFF CLEARANCESteven Natural Comfort Napa Leather Sneaker Mesh Panels GOLD & White 10 M NEWMerrell Jungle Moc Gunsmoke Walking Hiking Outdoor Shoes Suede Womens Sz 8?Skechers Women's Bikers-Hermosa Sneaker - Choose SZ/Color , shoes high-top sneakers fabric way JEANS violet PEPE JEANS T 39New Balance Women's W1540wPI Running Athletic Shoes Purple White Size-9 4ENike Air Climax Sneakers Gray Mesh Athletic Shoes Yellow Soles Womens Size 9.5M
"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."