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.Propet Women's Santa barbra Bronco Brown Slide Mule 8MAvec Les Filles Womens Genevie Open Toe SlingBack Espadrille FlatsTAOS US 10M Bungie Jump Brown Wrinkle Leather Slip on Mocs Loafers ShoesHOTTER Comfort Concept Chile Wmn 5 (US 7) Beige LaserCut Leather Mary Jane ShoeAEROSOLES QUATRO CINCHO Women Black Suede Mules Heels Slip Ons Slides Size 7.5 M , Born Lilly Wrap Toe Ballet Flats 455, Black, 6.5 US / 37 EU , Dragonfly Lightweight Slip-on Canvas Women's Casual Flats ShoesTherafit Gigi Women's Slip On Mesh Sparkle Casual shoes Sz 11, Silver , Nine West Womens Xalan Leather Closed Toe Loafers Black Size 5.0 YhY1 , NEW NATURALIZER MORRISON WOMENS COMFORT WIDE FIT CASUAL SNEAKER SHOESKenneth Cole Reaction Pro-Time Flats - Women's Size 8M - Black , Marc Joseph of NY Cypress Hill Snake Driving Moc Loafers Purple/pink size 7.5SANUK BLACK DONNA HEMP CHILL SIDEWALK SURFER SHOES, WOMEN US 6/ ~ NEWE15- New Balance for Nine West Shoes Size 9.5MASICS Gel-Kanbarra 5 White/Lightning/Apple Green Women's Sneakers 8MNAYA "Korthay" Ladies Slip On Sandal, White Leather, 8M MSRP $170Womens Breathable Sneakers Casual Athletic Running Walking Sports Shoes White US , Boden~Off White Canvas & Suede Tennis Shoes sz US 7.5 , Women's Fila Cool Max Memory Advance Energized Pink/Blk. Athletic Sneakers, SZ-9 , Asics Gel Cumulus 18 Women's Running Shoes Size US 10 B Blue Green T6C8NWomen's NEW STEVE MADDEN WOMENS GRADUAL Economy Athletic ShoesAdidas Terrex Agravic GTX Shoe - Women's Size 6.5 Blue , SHOES WMNS NIKE REVOLUTION 3 - 819303-009 , NEW IN BOX New Balance W880GP3 Women's US 7//White/Green/Purple 880NIKE WOMEN'S BLAZER LOW LX SHOES SIZE 6.5 silt red orewood brown AA2017 605 , RARE WMNS NIKE WORK FREE 5.0 ID BLACK-GREEN US SZ 6.5 EUC , Brooks Launch 3 Peacoat Teaberry Blue Red White Womens sz 7 B M Running Shoes , NEW Womens NIKE ZOOM W 4 Violet Middle Long Distance Track Spikes Shoes 9.5 10.5 , Adidas Rockadia Trail Women’s Shoes Size 6 New , Adidas NMD R2 Ivy Olive Green Grey White Pink Sneakers Shoes BA7260 Womens Sz 11 ,
"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."