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.Womens Ladies Flatforms Sandals Espadrilles Embellished Stud Jewel Wedges Size , Merrell Plaza Bandeau Taupe/Tan Suede Wedge Heel Mary Jane Shoes Women's Size 8 , Womens Faux Leather Sandal Comfort Loafers Casual Shoes / 2 Styles AvailableBOC brown, tan animal print clogs with 2" heel - womens 8 M, euro 39Very Volatile Women's Sz 6 Black Suede Leather Buckle Detail Loafers Shoes , Born Concept BOC Brown Leather Clogs BC6596 Mules Women's Size 8.5 M Shoes , Isaac Mizrahi Loop Tassel Nut Brown Suede Moccasin Flats New , NEW WOMENS ASHRO BLACK GIA WEDGES SHOES HEELS SIZE 7.5M 7.5 M , VTG RALPH LAUREN BROOKE SADDLE BROWN LOGO SLIPPER LOAFERS FLATS SZ 9 B , Unity Women's Crush Flat (6, Grey Croc)CORSO COMO PYTHON BALLET FLAT WOMENS NUDE CALF US SIZE 9.5 MEDIUM NEW W/O BOXNew Mi.iM MiiM Rebecca Free Beige Ruffle Trimmed Pointed Toe Mules 6 - 10 USZee Alexis Womens Norah Shoes Black Metallic 6 M , S.Oliver Slippers Sneakers Trainers Ballerina 24635 Jeans Blue Fabric NEW , Trotters Women's Amber Sand Soft Dull Leather D'Orsay 10 N (AA) , Womens UMBERTO RAFFINI YEVA sneakers shoes size 9 , Clarks Wave Black Leather Oxford Casual Athletic Shoes Women US 8.5 NWomens Flats shoes Round toe Pearls Winter Fur Warm Loafers Casual Pumps 2019 , Sugar Womens Granita Low Top Slip On Fashion Sneakers, Taupe Micro, Size 8.5 , Nike Sneakers Size 7.5 Running Shoes Grey and YellowSkecher Sport Premium Running Shoes, White/Silver, Leather,Women's US 9Women's Converse One Star Sequin Blue / White Fashion Sneakers SIZE 9.5 NEWSperry Top-Sider Women's Bahama Two-Eye White Cap Boat Shoe Pool Green 10 M USUnder Armour Women's SZ 8.5 Toccoa solder Overcast Gray Apollo Gray 6679  , PUMA Womens Blue Atoll Magenta TFX Star V2 Spikes Track Sneaker Shoes Size 7 , Brooks Glycerin 14 Grey/Aqua/Lime Running Shoe Women's US 9.5 Eur 41 (L2,1)Skechers Shape-Ups Adaptative Comfort-Ride Size US 9 women's walking shoesSkechers D LITES THIS JUST IN Womens Navy Memory Foam Sneaker Shoes , ASICS GT-2000 5 Running Shoes, Women's - Size 8.5, Black/Mint/Orange , Clarks Womens Glove Glitter Sneakers Neon Yellow Gray Size 10 ,
"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."