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.Theme Fushia Pink Croc-emossed Slip on Mule 9.5 NEW , Cream/Black Patent Leather Sperry Top Sider Loafers 8 M Leather Lined Nice! , PRE-Owned AK Anne Klein womens Lyndsy loafers shoes brown leather 7M DefectNEW WOMENS ANDIAMO PURPLE CASSIE SHOES SIZE 6W 6 W , Propet Tawny Women's Navy Leather Walking Shoes NIB 9.5 B (M) Casual Velcro , Banana Republic Black Breanna Flats Size 8 NEW , Sanuk Womens Pair O Dice Chill Slip Ons Black Size 9 New , Skechers Womens Bobs B-Loved Round Toe Loafers, Black, Size 8.5 DNcp , NIB Women's Ecko Skater Flats Shoes sz 11SAUCONY Shoes Athletic 10 White Pink Sneakers TennisSTEVE MADDEN Sneakers Black Leather Platform Size 7.5 US , GARDENIA - CHAUSSURES MOCASSINS TOUT CUIR MARRON 39.5 ITL 40FR - TRES BON ETATSAS Metro Super Suede Taupe Horse Bit Shoes Loafers Womens Size 9M , Penny Loves Kenny Women's Koi Fashion Sneaker, White, Size 12.0 g88x , Tony Little Cheeks Fit Body Ankle Sneaker Boot - Olive US 6.5Dansko Womens - Black Fashion Shoes Size 8 (335238)Merrell Capra Bolt Bright Red Women's Hiking Shoe 8MASICS Gel-Exalt Running Shoes Women’s 9 White Aqua Blue Athletic T35AQ , Reebok insta pump fury Women's Shoes size 11 Black and WhiteDr. Scholl’s Womens Anna TaupeChevronCanvas Walking Shoes Size 8 (361133)New Balance Minimus 10v1 Trail Shoe - Women's Trail Running SKU WT10GB Size 7 D , Fred Perry Aubrey Poly Womens Off White Textile TrainersWomens Nike Lunarconverge 852469-600 Lava Glow Brand New Size 8.5 , Dog Paws Print (Black/White) Running Shoes For Women-Free ShippingADIDAS ZX FLUX Running BLACK PURPLE WOMENS Training ATHLETIC SHOE SIZE 9.5 MWomen's Skechers - Graceful-GET CONNECTED - Gray/Coral - New!New Balance Womens White/Navy Cross Training Shoes Size 7.5 (14415)New Balance Women's W775GB1 Athletic Running Shoes Grey/BlueSalomon XA COMP 7 CS Women's Grey Denim/Stone Blue/Lucite Shoes 8.5MPuma Fierce Varsity Knit Grey - Womens - Size 8.5 B ,
"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."