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.Faded Glory Size 11 Sand Slip On Elastic Cushioned Insole Casual Shoes NWT**Jessica Simpson Nalan Flats - Women's Size 7 M - BlackWomen's Lands' End Green Suede Leather Slip On Mocs Shoes Size 7.5 M , Stuart Weitzman Gold Jelly Plastic Flats, Size 9, Beaded Toes ShoesCircus by Sam Edelman Snakeskin Ballet Printed Flats Sz 7.5 , Helle Romu's Women's Loafer Brown Gator Skin Buckle Size US 5, Moving AirBCBGeneration Xavier2 Bejeweled Slip On Ballet Flats 490, Pewter, 9.5 USRebecca Minkoff Shoes SZ 9 Mika Shoes Slip On Gold Mule Slide Flat NIBNEW Sperry Top-Sider ANGELFISH Black Gray Deck Shoes $90 6 S , NWT $119 Klogs Leather Naples Black Nurse Medical Clogs Shoes 7 M , DANSKO WOMEN'S OLIVIA SLIP-ON FLATS METALLIC LEOPARD SUEDE 39-8.5 MEDIUM EUCNaturalizer Size 8 Brown Womens Gadget Slip On Casual Leather Loafer $129 New , Crocs Freesail Graphic Clog Female Ballerinas Synthetic Leopard MulticolorLauren Ralph Lauren Clarana Women's Ivory Shoes Leather Slip On Loafers 8.5 BEcco Lynx Casual Shoes, Women's Size 41 (US 10-10.5), Black , Melissa & Karl Lagerfeld Trippy Flats, Women's Size 7, Black , LL Bean Sneaker Oxford Women size 10 Brown Suedenew balance women shoes size 7.5 , GIRLY GIRL Keria Women Size 7 White/Black Sneaker Shoes , Easy Spirit Kelt walking shoe wedge loafer wine Breathable GEL 10.5 Med NEW , Women Faux Patent Leather Large Bow Skimmer Flats Shoes , Skechers Women's Shape Ups Fitness Walking Toning Workout Shoes Size 7 WhiteWOMENS SAUCONY GRID EXCURSION TR8 BLACK BLUE RUNNING SHOES SIZE 10W G799Men's Shoes Slippers Mens~Levi Strauss~Houseshoes~Slippers~Size 9-10~Fabric~ Quality Products Slippers , ASICS Womens - Blue Running Shoes Size 9 (326535) , NIKE AIR VISI MAZY VINTAGE RED WHITE HUARACHE WOMEN WMNS SZ 7.5-10 302420-611 , DREW Women's 9M Athletic Barefoot Freedom Sneaker NWT Retail $144.00 Nice A13 , Vans Sk8-Hi Slim Zip Womens Croc Emboss Hemp Blanc D Blanc Suede Shoes Size 9.5Salomon XA Comp 7 Women's Detroit/Autobahn/Bordeaux Trail-Running Shoes 10M , Nike Air Max Thea TXT Womens Running Training Shoes Size 9 White Gray
"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."