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.Dana Buchman Size 7.5 Deep Pink Die Cut Man Made Ballet Shoes Women FlatsLL Bean Slide Shoes Size Women's 6 - Brown SuedeWOMEN'S Studio Paolo SCARLET SliP On MULTIPLE COLORS/SIZES MSRP$35-$39 NEW IN BWomen's Very Volatile Sz 8 Brown Clogs. Animal Print. WS204DR SCHOLLS BROWN WOVEN LEATHER SLIP ON MULES/CLOGS FLAWLESS sz 7 MABEL , COLE HAAN Sara Air Womens Size 10 Brown Suede Leather Slip On Clogs Mules ShoesMIA BLING Bedazzle Buff Gold FLATS Shoe 7.5M Slip On NEW CLASSIC CHIC HOLIDAYBirki's by Birkenstock Blue Mules Slides Mary Jane Comfort Size L 7New Y.R.U Lowf Panther Flat women's shoes size US 9 , size 7.5 Lucky Brand Emmie Black Karite Ballet Flats Womens ShoesCLARKS Women's Grasp Chime Slip-On Loafer Black/Black Patent Size 6.5 gwURDerby PEDICONFORT Cuir Gris Taupe T 38 TTBELADIES SPOT ON TRAINERS WHITE/MINT STYLE - F8981FitKicks Gray Purple Womens Small Active Lifestyle Footwear Shoes 5.5-6.5 TravelSteve Madden Womens Jill Penny Loafer Mule Shoes Red Multi US 6.5 , Sam Edelman Kollins Women's 7 M Black Haircalf Chain LoafersNew Balance Running Shoes Black Synthetic Women8Medium (B, M) , Womens Summer Breathable Hollow Out Height Increasing Sneakers Casual Shoes ThinNIKE FLEX TRAINER 7 SHOES WOMEN'S SIZE 9.5 , Reebok Classic Harman Run W Bare Beige/Chalk/Chalk Pink Womens Running Size 9.5MSaucony Women’s Ride 8 Pink Blue Running Shoes Trainers Size 8 Medium Used. , New Balance Fresh Foam 1080v7 Running Shoes, Women's Size 7.5, Blue/Yellow , Nike Max Air 180 Rare Vintage Airmax Revolution Lime History of Air 2005 6.5Steve Madden Grey Multi Natural Comfort Whales Sporty Sneakers 9 NEWPuma Women’s Black Fierce Core Casual Sneakers Size 7Reebok Womens White V61774 Walking Shoe Size 9 wideD , 7.5/38 GUESS Sport Feather Weight Pink Athletic Running Walking Shoes SneakersWomen Size 9 Nike Flex TR 5 White Orange Training Running Shoes A2310 , Fire Sale Clearance- Sam Edelman Women's Carleigh Sneaker- 9.5. Color BlushNew Balance 1540 Heritage Collection Womens Size 10 Black Running Shoes W1540BK1 ,
"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."