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.Ladies Women's Hidden Wedge Velvet Ballerina Ballet Flat Shoes Comfort Heel Lift , EASY SPIRIT SHOES WOMEN'S SIZE 9 B , CLARKS WOMENS BLACK LEATHER ZIP SIDE ANKLE BOOTS LOAFERS SIZE 9MEasy Spirit - Women - US 6 1/2 M - Tan - Pre Owned - ELISAS - 1009BOC Born Women's Shoes Clogs Pumps Wedges Leather Black Glossy Slip Ons Sz 38.5Women's Clarks Bendables Black Leather Casual Loafers US 6 M , Lucky Brand Womens Shoe Enorahh Laser Cut Perforated Flat Glazed Kidsuede 6.5 M , SAS Beige Slip On Loafer Womens Size 6.5W , Fashion Women Casual Shoes Air Mesh Flats Shoe Slip-on Comfortable Casual ShoesCamper Scarlet Red Leather Mary Jane style comfort shoes, sz. 38 (8 US)ABEO BIOSYSTEM "MARILEE" Blue Leather Driving Loafers Shoes Women's Size 6 NRaffaella Venturini Black Leather Rounded Toe Oxford Shoes Size 40 10 , MERRELL BLACK LEATHER “PRIMO CHILL” SLIP-ON LOAFERS WOMEN’S SIZE 8 XLNT , womens monet victoria platinum slip on flats shoes size 9 1/2Klogs Natalie Womens Leather Clogs Display Model Hands 6 M , STEPHANE KELIAN Derby Vintage à Boucles Tout Cuir Tressé Noir T 35 TBE , Sperry Authentic Original Sahara Boat Shoes - Women's Size 7 W - Tan , Giani Bernini Womens Odeysa2 Leather Closed Toe Loafers Hibiscus Size 12.0ROCKET DOG Women Athletic Walking Shoes Size 8.5 Silver Leather/MeshReebok Womens Tennis Shoes Memory Tech LT Prime Size 9.5 Black RunningNEW NINE WEST "DOPPIOGO" OLIVE TENNIS SHOE, RARE SIZE 12Women Cobian Leucadia Flip Flop Sandal LEC17-965 Natural 100%Authentic Brand New , DKNY Brayden Binding Fashion Sneakers 980, Tan, 8.5 US / 39 EU , New Balance Men's CLASSIC 574'S silver mint moonbeam ML574OUCNEW Beloved WOMENS HIGH TOPS SHOES CATS US 6-12 CUSTOM MADE TO ORDERNike Mayfly Lite Pinnacle Women's Running Training Shoes Thunder Blue 881197 400 , Nike Primo Court BR Womens Athletic ShoesGamma 833678 441 Blue Teal/White NIBNew Nike Womens Lunar Sculpt Run Running Shoes 818062-500 Purple Smoke sz 7 , Womens Nike ROSHE TWO HI FLYKNIT Boots -Retail $225 -861708 002 -Sz 7 -NewSteve Madden - Ecentrcq Sneaker - Black - Size 8.5
"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."