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.Rockport Loafers Caramel Suede Shoes 6 M BrazilRefresh Blue & Gray Woven Material Light Weight Soles Women’s Sz 10 New , DR. SCHOLLS Wome's "Hadley" Brown Slip-On Loafers Size 10Womens 10 M Joan & David Hand Made Italy Brown Leather Brogue Wingtip Shoes FlatZALO MULTI-COLOR COTTON UPPER MADE IN SPAIN SIZE 7.5 MSanuk Funky Fiona Women's Shoes Grey Tiki Print 9 , Charles Philip Ballet Flat Sheila White Leopard Print Sz 6.5 Matte Satin Slipper , Skechers 22836 Women's White Lacy EZ Flex 2 Sport Active Shoes Size 8M $60New Womens Enzo Angiolini Flats Leather 7N 7 N Narrow Dark Blue Shoes Loafer , Bandolino Women's Fadri Ballet Flat, Black, Size 6.5 u0mW , ALEGRIA GLE-681 Women's Black Swirly Silver Strap Slip On Flat Shoes Sz39 SZ 9 , RANGONI Firenze Womens 8 Shoes Black Leather Loafers MoccasinsKLOGS BAMBI WOMEN'S DISPLAY MODEL SHOES GRANITE WIGWAM 8.5 M328C Rag & Bone Standard Issue Beige Suede Embroidered Diamonds Sneaker Sz 38.5M , 2017 HOT Women's Sports Running Shoes Shock ABSORBING Trainer Sneakers shoesWomen Suede Flats Slippers Mules Silk Bow-knot Slides Rabbit Furry Size EU35-39Dr. Scholls Women's Gel Insole Shoes Size 10 White Pink Sneakers Mesh NWOB SlipWomen's Purple Star Print Chuck Taylor Hightops, Size 9New Balance Womens Sz 8.5 WARISCK1 Black Running Training Athletic Shoes F5-313 , New Women's Skechers GoWalk 3 Unfold Sport Causal Style 14047 Black 301U lr , Women's Mia 2 flats Beautiful FlatsNike Womens AF1 Ultra Force Mid PRT Athletic Snickers Shoes Size US 6.5Nike Women's Flyknit Lunar 2 - Bright Mango/Game Royal/Black (620658-800)Brooks Launch 5 Black/Purple Running Shoe Women's US 9.5 Eur 41 (F4,10)Adidas Women Shoes Arianna Cloudfoam Running Training Fitness Gym BB3243 New , New Balance Womens - Gray Running Shoes Size 6 (363309) , New Balance 990 Pink Gray Sport Running Training Shoes Women's Size 10.5 , Salomon Synapse Women’s Ortholite Shoes Hiking sz 6NIKE Zoom Rival MD 6 Cleats Track & Field Spikes 468650-503 Women's Size 8Puma Fierce Bright - White - 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."