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.Women's Tavoy Black Jeweled Velvet Low Heel Pointy Toe Loafers Size US 9.5 B , Bella Marie Womens angie53 Fabric Pointed Toe Ballet Flats Black Size 8.0 , NEW LAND END'S GRAY OVER BLACK SUEDE 7 1/2 B WOMEN'S SHOESTEVA Women's Ancona 6918 Black Leather Loafer Walking Shoes Mary Janes sz 10 , Munro American Carrie Women's 7.5 W Black Croc Print Leather Loafers ShoesAlfani Womens Gessey Closed Toe Slide Flats , DOUBLE H BOOTS Women's Brown Leather Slide Mule Clog Western Shoes Size 6 / 36.5Women's Soft Style Fairfax Sneaker - Rose Quartz Synthetic Sneakers Size 8M , Cole Haan Womens Shoes Sz 6 Plum Purple Patent Leather Heels Loafers , SoftWalk Women's Norwich Ballet Flat, Pewter, 7.5 N US , Womens DANSKO Brown Leather Clogs Shoes SIZE 41 US 10.5-11Baby Phat Blake 2 Women's Black/Fuchsia Sneaker 8MSam & Libby Edelman Black Size 8.5 SOLID Velvet Bow Shoes , VANELi Women's Stevie Flats Shoes, Black, Size 8.0 RZCg , Ellen Tracy Womens EB-BUFFY Open Toe, BUTTERCUP/BLACK, Size 7.0Saucony Originals Jazz Low Pro Athletic Shoes - Women's Size 9 - BlueWOMENS VANS Size 8 Gray TB4R Canvas Sneaker Shoes Skateboarding , K-SWISS Women's WHITE/SHOCKING PINK MEMORY FOAM Lifestyle TRAINER Sz. 9 , Saucony Womens S10373-3 White Blue Walking Shoes Size 9 (24428) , NIKE Free TR Fit SNEAKERS Sz 7 Pink Red running workout shoes training Q2 , disney evil queens inspired HIGH TOPS HAND PAINTED MADE TO ORDERBrooks Pure Flow 2 Diva Pink / Anthracite Black Running Training Shoes-Size 7.5Skechers Women's Relaxed Fit Bikers Get With Knit SneakerAdidas Maduro Running Women's Shoes Size 7.5 , Women's Skechers - Synergy-Trend Setter- Black - EW - Wide WidthsWomen's Puma Speed 300 Ignite White-Rose Red-Peach 18811501 Brand NewWomens Skechers Unity - Existent 23074 Stone/Navy , Sketchers Shape Ups Size 6 Womens Clean Blue White GrayVintage Womens Nike Air Max 120 Wmns 8 Blue White Yellow 174168-141
"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."