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.2-Yellow Box Suede Boat slip on shoes Brown & Leopard print ladies size 7.5 M , TALBOTS Tan Leather Snake-Embossed Ballet Flats Size 6.5 B Rubber SolesSperry Top-Sider Angelfish Black Patent Leather/Zebra Sequined Boat Shoes - 6.5M , COLE HAAN NAVY BLUE TASSEL SLIP ON LOAFERS WOMEN'S 9AAAA ld , Fashion Lightweight Slip-on Canvas Casual Flats Shoes for Women Butterfly SkullsClarks Artisan Leopard Womens Driving Loafers Flats Bow Hair Shoes Size 8 MLadies Long Tall Sally Ballet Flats Brand New Size 12Kenneth Cole New York New Willow Beige Womens Shoes Size 6 M Flats MSRP $170Salvatore ferragamo Women Excellent Condition Suede sandals 8.5 aa , WOMEN'S SKECHERS BLACK MARY JANE SHOES SUEDE LEATHER & TEXTILE SIZE 8ADIDAS By STELLA McCARTNEY FLORISUGA FLAT, Navy, Size 8MNordstrom Size 6.5 M Brown Patterned Leather Pump Squared Toe 2.25" Heel , Dansko Womens Professional Textured Leather Dazzle Clog - Black US 6.5-7NATURAL WORLD Womens ART 805 Black Sustainable Boot US 6.5; (2800095255402)Reebok Womens Reeshift DMX Ride Work Sneaker Slip Res WIDE White All SizesNew Balance Women's 928 Walking Shoes White/Grey Size 6 2E X Wide GUC , SKECHERS SHAPE-UPS 8.5 BLACK/White 11809 TRAINING TONING WOMEN'S SNEAKERS , New Balance WW927WT Women's Athletic Walking Shoes Rollbar Size 8Women Hidden Wedge Fashion Sneaker Slip On Breathable Oxfords Casual Shoes 2018New Converse All Star Chuck Taylor HI 549636F Gold & Black Womens Feather , Merrell Womens Taupe Running Shoes Size 7.5 (9121)NEW Womens NIKE Air Force 1 Low Canvas Green 2008 DEADSTOCK Sneakers Shoes , Clarks Women's Brizo Cady Active Sandal Black/Grey Textile Hook and LoopVince. Warner Gray Womens Shoes Size 9 M Flats MSRP $250 , Skechers GOwalk 3 Navy Slip-On Comfort Walking Sneaker Woman size 9.5 NEWASICS Gel-Venture 6 Womens US sz 10 Trail Running Shoes Black Carbon Mint GreenVasque Women's Trailbender II Size 10 US Ebony/Mint (VS18W-Misc)Altra Womens sz 9 M Provisioness 2.0 Gray Purple A2544-1 Zero Drop Running Shoes , Women’s TRAVEL FOX Low Cut Shoes Sportivesseme Eur 37 US 6.5 Mesh Patent Leather , Speedo Women's Hydro Comfort 4.0 Water Shoe Black/Hawaiian Ocean 6 C/D US
"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."