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.Hush Puppies SHOES WOMENS SIZE 9 M , NWOB Brash Black White Open Side Point Toe Flat - Plaid Women's Size 7.514th & Union Beige Faux Leather Open Side Cutout Flats Shoes Size 7M MINTEasy Spirit Women's Geinee Slip On Loafer, White Synthetic, 10 M US , Dansko 40 9 Professional Clogs Burgundy Red Leather Stapled Shoes Womens NursingClarks Everyday Women's Brown Suede W/Reptile Print Loafers Size 8.5 , Cole Haan Lunar Grand Women Size 9 Oxford Wingtip Black Brogue Leather CasualNew JAMBU JBU Juniper Ballet Flats Mary Jane Black Vegan Leather sz 7.5MWomen's Cole Haan D18611 Mules Flats Shoes Size 7B Black Leather Career Dress E8DONALD J PLINER Black Patent Leather Mocs Loafers Women's Slip On Shoes Sz 7 M , 7 Ivory Cream Beaded Shoes Jutti Silk Indian Sari Khussa Wedding Bridal Flats , Tesori Womens Black Shoes 8 W , Alegria Black Vine Rocker Wedge Mules ALG-921 Womens Size 37 7 / 7.5 , Tripad SAS Comfort Foot Bed Womens Size 7Women's Aldo Clogs Size 39 US Size 8.5 , Sperry Top-Sider Women's Bahama Fish Circle TPE Fashion Sneaker Taupe 5 M USNew Free People Letterman Platform Sneakers women's shoes size US 8.5-9y SAS VIVA Women Black Leather COMFORT TRIPAD Shoe SOFT STEP Loafers 9.5 1/2 N , BOBS from Skechers Womens Bobs Alpine-SMores Ankle Bootie- Pick SZ/Color.Delman 7.5 Gold Metallic Loafers Flats Great condition made in Spain leather , DREW 10202-1P Women's Size 12 WW Tulip Black Croco Patent Leather , Fashion Women Embroidery Floral Hidden High Heels Sneakers Casual Creepers Shoes , PUMA MODERN SOLEIL-W Womens Modern Soleil Sportstyle Sneaker- Choose SZ/Color.New Womens Lady Breathable Hollow out Platform Athletic Sneakers Casual ShoesWOMENS SKECHERS GO WALK SHOES MEDIUM & EXTRA WIDE AVAILIBLE-SEE SIZES (385) , Women's Nike Air Max 1 Ultra PRM JCRD Metallic Silver Black 861656-001 NEW $140Women's Asics Gel-Pursue Lighting Purple Lime Running Shoes T498N sz 8.5Nike Lunarglide 8 Running Shoe- Women's US 9.5 Medium BlueZee Alexis Womens Danielle Athletic Shoes Black Teal Multi 6.5 M , adidas Courtset - Black - Womens
"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."