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 Rockport Shoes, Red Leather Loafers, Made in Brazil, Size 8 1/2 M. Classy , Cole Haan Women's Size 7 B Air Waterproof Rain Shoes Brown Patent Leather Zip UpTod's Black Patent Leather Loafers Shoes Sz 7.5 , Vintage Aerosoles Ukraine Navy Leather Casual Flats Rubber Soles w/box 8.5BSkechers Women's EZ-Flex-3.0 Sweet Garden Memory Foam Loafers Shoes , Tory Burch Women's Aaden Brown Beige Leather Suede Gold Logo Flats Sz 5 1/2Mercanti Fiorentini Sz 5.5 M Penny Keeper Brown Leather Loafers New Womens ShoesNew DONALD PLINER Gunmetal CELEST Slip-On Sneakers 6 M $168 NIB Leather , ARA PAM Shoes GORE-Tex Gore tex slip on Black Comfort Loafers size 6 M 3 1/2 3Women's Cole Haan Slip On Shimmer Blue Wedge Size 7.5Trotters Womens Estee Closed Toe Ballet FlatsVince Camuto Womens CIANA Leather Closed Toe Oxfords khaki Size 8.5 , ASOS Trainers Black White Camouflage Python New , new women round toe slip on tassel patent leather block chunky heel shoes loaferChampion Women Wrestleling Shoe Athletic Sneaker Black and Pink Size 11Converse Chuck Taylor All Star Suede And Faux Shearling Low Top Womens Size 9.5 , ASICS GEL-FLASH JOG RUNNING WALKING Women's Shoes Size 9.5 US T2J5N , Women's Mizuno Wave Rider 20 Gray and Pink Shoes Size W 8.5 , Puma Rudolf Dassler Women Shoes Black Leather Suede Fashion Sneakers Sz 42 US 10Reef Women's Escape Lux Flip Flop Coral Waterproof , Steve Madden Womens Kickstart Black Fashion Sneakers 9.5 Medium (B,M) BHFO 5345Skechers Skecher Street Womens Side Street-Rock Glitter SneakerSkechers Skyline Navy Womens Sporty Shoes Size 10MVANS ISO 1.5 True Red/True White UltraCush Trainer Women's Shoes Size 9Authentic Used With Box Liz Lisa Black Size L Gyaru Suede Back Ribbon Sneakers , Women's Skechers Go Run Fast Invigorate - Black - Width: med - Cross Training , New Balance WX867BK Women's Black and pink Cross Training Sneaker 6 B MINTBaskets GEOX Patent Cuir et Textile T / T 37 EUR / T US 5 BEAdidas Pure Boost X Women's Raw Purple Shock Red Running Shoes Size 10 , Fila Women's Fulcrum 3
"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."