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.CLARKS Cloudsteppers Black Slip-On Loafer/Flat Sz 8 NIB!VIC MATIĒ Leather Sneakers Size 36 Rabbit Fur Slip On Made in ItalyChristian Siriano for Payless Women's Tan Chopout Women's Delilah Square Toe ...BELLISSIMO BEAMING WOMENS LEATHER SLIPON LOAFERS SHOES/CASUAL/SOFT & COMFORTABLE , BASS & Co "WALDORF" Penny Loafer Burgundy Low Wedge Sz 7.5M Womens ShoesROS HOMMERSON Flats Loafers Size 4A Black Stretch Material Leather 37210 , NWB Aerosoles Trend Report Crochet Fabric Loafer Shoes Women's SZ 7.5 M Black , Rocky 4EurSole Fushia Pink Patent Leather 3 in 1 Work Comfort Clog Shoe NEWColumbia Women Jute Green Denim Slip On Flats Sneaker Comfort Size 8Talbots Shoes Brown Flats Womens Size 6M DeirdreDonald J Pliner Black Patent Leather Trim Platform Shoes Size 8 MDr Comfort Womens Size 10 Beige Leather Merry Janes Diabetic Therapeutic Shoes , Butterfly Twists Jade Flats-Women's size 8 Black , NEW SPERRY TOP-SIDER BISCAYNE BOAT SHOES WOMENS 9.5 BLUE GREEN FREE SHIPNaturalizer Davonville Womens Blue Beaded Aztec Espadrilles Flats Shoes Size 8.5 , CREATIVE RECREATION GOLD/WHITE/BLK HIGH TOPS SIZE 7LCONVERSE Women Light Low Black White Plaid All Star Sneaker Canvas Shoes 513759FSaucony Ride 10 Running Shoes, Women's Size 7.5, Grey/Silver/Pink (Damaged)EUC Women's Nike Air Trainer Total Core TR Green And Blue Size 6QAUPPE Women's Casual Tennis Walking Shoes Lightweight Mesh Athletic Slip-On 10Fashion Womens Mens Canvas Sneakers High Top Casual Trainers Comfy Unisex Shoes , Olukai Nohea Mesh - Girl's Pale Grey/Dk Hibiscus - 3 M US Little Kid , Puma Women's Match Lo Bw Training ShoeAdidas Turbo 1.1w Running/Course NavyBlue/Pink/Red Women’s Size 7.5 , ALDO Women's MX.2B Sneaker, Light Blue, 9 B US , New Balance WX867BK Women's Black and pink Cross Training Sneaker 6 B MINT , VANS CAMRYN SLIM NATIVE TAOSE TAUPE OMBRE BLUE MIDTOPS VN00SDVG1G WOMEN'S SIZE 5Nike dunk low WMNS size 11 retro rare authentic VTG skateboard OG QS classicRYKA Women's Dash 2 Walking Shoe - Choose SZ/ColorNew Womens Shoes Fashion Casual Sneakers 8.5 White Black Skecher Street Disco ,
"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."