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.Doctor Scholl's Black Leather Vienna Slip On Flats Women Size US 6.5M $0.99 SaleCROFT & BARROW BLACK LEATHER SIZE 7 1/2 LOAFER SHOES , Clarks Unstructured Un.Block Olive Leather T-Strap Buckle Loafer Womens Sz 6.5 MBorn Women's 8 / 39 Suede Slip-on Loafers Heels Shoes, W91011 CIJ10 M/W , EARTH ORIGINS Womens LONDON Leather Round Toe Ballet Flats, Black, Size 9.5 elicSuperga Size 5 M Fantasy Denim Blue Espadrilles New Womens Shoes , Comfort Life Mary Jane Hook & Loop Cut Out Red Leather Sandals Shoes Women's 10 , GEOX Respira Black Patent Leather Croc Embossed Rhinestone Shoes, Sz 38 , Ladies Hi-Tec Casual Trainers Shadow Original , Womens Sperry Off White w/Blue Stripe Down Back Canvas Sneakers Size 75M (X162) , Grey Gray Canvas shoes sneakers Mossimo size 6 Kids GirlsGray Vans Skater Textile Upper Shoes Women's Size 10Mordenmiss Women's Candy Color Mori Style Loafer Step-in Casual Play Shoes 39... , DIESEL EVELYN WOMENS LEATHER FASHION SNEAKERS SHOES SIZE 5 , Nike Air Max 90 orange/white/gray Running/Tennis Shoes Size 7 , Donald Pliner Slip on Sneakers Womens Size 7 Black , Women's Womens Sketchers FLEX Size 10 Big Clearance Sale Athletic Shoes , Women's LifeStride Women's Gita Slip-On Loafer, Trendy Flats , Aerosoles Sea Salt Womens Fashion Sneaker- Choose SZ/Color. , Pin Up Couture Women's Smitten 20 Mary Jane Pump Dark Brown Faux Leather HeelsBRAND NEW Adidas Pure Boost Xpose Running Silver Shoes Women Size 9 BA8268Skechers Bikers Skim Running Women's ShoesMizuno Wave Hurricane - Black - Womens , Skechers Sport Womens Ez Flex 3.0 Estrella Fashion Sneaker- Pick SZ/Color.Skechers Shape Ups Womens Size 7 Brown ShoesConverse Men's Chuck Taylor All Star Tie Dye Low Top Sneaker - Choose SZ/ColorWomens Gray Nike Free Xilla Run 5.0 size 9NEW IN BOX WOMENS NIKE REVOLUTION 3 RUNNING SHOES SNEAKERS SIZE 6New Women’s Nike In-Season TR 6 Sneakers Training Shoes Size 11 Gray/White/GreenKaty Perry Womens the heart sneaker Leather Low Top Slip On, White, Size 9.5 hU9
"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."