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.New women's shoes ballet flat ballerina synthetic casual summer pink fuchsia , Rocket Dog Spotlight Solar Power Oil Slick Womens Flip FlopsSALE LADIES UPDATE BROGUE STYLE SHOE IN TAN PU, COFFEE PU AND BLACK PU L4912 , Dansko Diana Brown Leather Mary Jane Shoes Size 39 US 8 WomensJ CREW DARBY STUDDED GOLD BEIGE LOAFERS LEATHER FLATS SHOES 8M W/ BOXFranco Sarto Rosita Suede Slip On Clogs Shoes in Le Mushroom Size 9.5 MMARCO TOZZI Ballerinas Slipper Shoes Court Shoes Espadrilles White NEW , Tommy Hilfiger Womens Frank8 Suede Closed Toe Mules, Navy, Size 7.5 VgBvBoden Alice Flat Navy Purple Aqua Size 7.5 M , Bobbies Womens La Romanciere Glitter Oxfords Shoes Grey Blue Size 39 NewClarks Candra 6.5 Bronze Ballet Flats Women's Slip OnMarc Fisher Barnum2 Rhinestone Espadrilles Flats, Light Natural, 7 USPropét SHOCK ABSORBER WALKING BLACK SHOES WOMENS SIZE 7 1/2 W(D)Womens Casual Breathable Platform Wedge High Heel Sport Ankle Boots Sneakers US8Fashion Fringe Women Rhinestones Loafer Platform Conceal Athletic Shoes SneakersWomen's mens leisure high top work shoes round toe breathable us5-12.5 outdoor , Converse CTAS Madison Ox Women’s Size 7 Black/White/Vivid Pink Sneakers TX-31 , Nike Womens Lunar Converge White Running Shoes Size 10 (425269)Women's NEW REEBOK WOMENS PRINCESS LTHR Outlet Online Athletic ShoesPuma Basket Platform NS Wn's SZ 9.5 Icelandic Blue 364587-02 , Xero Shoes Lena Black Canvas Barefoot Inspired Sneaker Women’s Sz 7 , Adidas Neo Women's Courtset Sneakers B74561 Trainers Athletic Shoes Gray Size 9 , Puma Women's Basket Jewels Suede Fashion Sneaker Whisper WhiteWomens Asics Running Shoes White/Medieval/PurpleHaze TN065 Size 6 B - NIBNew FILA Womens SLEEK AQUA SHOES LIME FS1WAA2013X WATER SHOES UNISEX SIZE TAKSEHoka One One Women's Challenger ATR 3 Athletic Training Running Shoes Size 8.5 , Tretorn Marley HI2 Sneaker- Women's Size 4.5 M, Gold , Naturalizer Charlie Satin Platform Sneakers, Women's Size 4 M, Pink , nike shoes women size 9 new , Mizuno Womens Wave Inspire 10 Running Shoes, White/Black/Blue, US 6 Wide ,
"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."