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.Salvatore Ferragamo Brown&Black Leather w/Fringe Bow & Brogue Detail Loafer 8AAASeychelles Women's Brown PerforatedLeather Slip On Slim Ballet Flats US Size 8CLARKS ORIGINALS Faraway Meadow Women's Sz 7 Light Beige Leather Slingback Flats , 86% OFF New WALKING CRADLE ELITES Regan Moc Loafer Black Viper Leather sz 5 $169SAS Free Time Mocha Leather Tripad Comfort Walking Shoes Women's Size 9.5N $157Women's G. H. Bass Co. Brown Woven Leather Casual Slip-on Flat Shoe - Size 5MWomen Lady's Shoes Flat Shoes Casual Shoes Athletic Sports Running Shoes Trainer , 6D 6W Black Patent Leather Ballet Bow Flats Ballerinas Varina Classic ShoesAthena Alexander Women's toffy Ballet Flat Tan Suede Size 10.0 , NAOT Otago Loafers Black Leather Women 39 / 8 MNEW Clarks Collection Womens Shoes Size 8.5 Brown Textured Wedge Loafers Casual , EVERYBODY, MODERNA MOCCASIN, WOMENS, BLACK, US 9.5M EURO 39.5, PRE -OWNEDKlogs Martha Womens Clog Shoes Display Model Leather Black Grey Flower 10MTSONGA ~ WOMEN'S SUEDE CLOG ~ DARK BROWN ~ SIZE 8MFitFlop Superskate in Velvet Shoes - Women's Size 8.5 - BlueCrocs Kadee Slip On Comfortable Ballet Flats Women's Size 8 Black NWT (S910)Sperry Top-Sider Grayson (Ivory Canvas) Women's Slip on Shoes 9507286 Size 6mNew Women PU Satin Bow Tie Low Top Sneaker - 17926 By Refresh CollectionRockport $90 MEN SHOES SLIPPERS Suede Moccasin Slippers SIZE 10 Black SALE P16Rj'S Genuine Sheepskin Men's Scuff Slip-on Slide Slippers Black Medium (D, M)Mens Slippers Grosby Hefner Black/Kahki Summer Slipper Scuffs Adhesive Tab S-XL , New Steven By Steve Madden Catie Slip-On Black Size: 8Animal Pet Fashion Women Running Trainers Mesh Sports Shoes Athletic SneakersASICS Women's Gel-DS Trainer 22 Running Shoe Purple/White/Yellow Size 7.5M , Women's Nike Flex Run 2016 Womens A Great Variety Of Goods Athletic ShoesNEW Nike Women's LUNARTEMPO 2 Print Persian Violet/Total Crimson-Gamma Blue SALENew Women's Puma Fierce Bright - 189738-04 - Peacoat Navy Sneaker , Easy Spirit Felidia Walking Shoes - Women's Size 8.5 M - BlackVans Asher Women’s Size 8.5 Multi Cloudwash Canvas Casual Sneaker Shoes F3-184 , Fila Memory Statique Women's Running Shoes Sneakers
"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."