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.Sidekicks Foldable Flats with Case NWT Various Styles and SizesWomen's SBICCA of California Black Leather Loafers Slip ons Size 9M ShoesAravon Womens Oxford Size 8 B Black Leather Slip On Comfort Shoes Web 01 BKcrocs Crocs Womens Ballet Flat- Select SZ/Color. , Soft Style by Hush Puppies Women's Faeth , Skechers Bobs High Jinx Wedge Shoe Black NewRieker Ballerinas, Slippers Leather/Textile Black/White NEW , British Womens Girls Literary Rhinestones Loafers Slip on Creepers Shoes CasualWomen's Sperry Top-Sider Rainbowfish LL Black Boat Shoe Size 5.5 , Official eBay Branded BOPP Packaging Tape - Packing & Shipping - 1 RollBrooks Ghost 6 Womens Running Shoes size 5.5 Gray/neon YellowRYKA WOMEN'S TAN -- MESH / LEATHER WALKING SHOE'S TAN SIZE U.S. 6 , Propét Women's Wash N Wear Slip On LL Walking Shoe 8.5 2X Wide Merlot SuedeSperry - Sky Sail Canvas Sneakers, Women's Size 5 M, White , Skechers Shape Ups 11807 Toning Walking Mary Jane Shoes Women's 8.5 VERY GOODWomen's Sbicca Women's Rafa Sneaker Sale Price Athletic Shoes , Women's Converse CTAS LEATHER+FUR Chelsea Boot 553393C Size 7 Maroon White BlackEasy Street Women's Kindly Espadrille Slingback White Floral Synthetic Sandals , Nike Zoom Rival XC Women's Bold Berry/Mint Foam/Light Magenta 04717503Saucony MEMORY FOAM TECHNOLOGY Women’s Size 7 RUINING SHOES ,Eur 38 , Onitsuka Tiger Ultimate 81 Classic Running Shoe,Charcoal/Black/Black,4.5 M USConverse Women's Chuck Taylor CT AS Fancy Supernova Wash Shoes Black , New Balance Womens Wxnrg-Sm Gray Fashion Sneaker Size 7.5 (C,D,W) (28352) , Nike Ultra Comfort Thong Women's Black/White 82697001 , Fila Size 11 MEMORY OUTREACH Grey Running Athletic Sneakers New Womens Shoes , Altra PARADIGM 1.5 Zero-Drop Womens Sneakers A2535-4 Black/Aqua Blue Size US 7Skechers Women's Endeavor-Venturer Taupe Fashion Sneaker - Size 7 / 8 , Nike Air Trail Alvord 4 Gray Womens Sneakers Athletic Jogging Xfit Shoes 10 42 , New Vans Winston Women's Skate Shoes - Tropical Floral - Size: 9.5 , Women Athletic Sports Sneakers Outdoor Running Jogging Navy Shoes 1704 a_C
"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."