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 THE SHOE TAILOR GOLD LOAFER SHOES-SIZE: 8EEEEE , Women's Rockport Shoes Pearl Color Shimmer Size 9 1/2 MSz 8 - Mark. by Avon Women's Black & White Flats Slip Ons Pointed Toe , new Cole Haan red suede ballerina slippers Sz S , Merrell Midnight Black Suede Jungle Moc Shoes Women's 7.5 , Skechers Womens Perfect Patch Canvas Round Toe Slide Flats Camouflage Size 5.0Sam Edelman Black Flats - Felicia- Ballet Shoes -Work Size 1 M (5) , Marc Fisher Jodi Cap-toe Ballet Flats Pointed Toe Slip On Black 6M NEW S8139 , Skechers California Luxury Vaso Bonita Slip On Shoes, Women's Size 9.5, Black , Klogs Missy Womens Clog Shoes Display Model Brown Croc 9.5 M , Sperry 9349473 Boat Shoes Silver Blue Womens Size 9.5M , 1803 Ladies Amber Brown Suede Leather Comfort Shoes 37 US 6.5 , NEW Madden Girl Crystal Embellished Flat shoes SIZE 9 Gorgeous!!VANS Casual Sneakers, Black/Turquoise/Pink, Canvas, Women's US Size 8.5 , Charles David Silver Blue Leather Sneaker Shoes Size 9 Futurist $180 retail , Mossy Oak Tree Camouflage Memory Foam Slippers ~ Size XL(13/14) , Keds Multi-Colored Canvas Women's US Size 8.5 Comfort ShoesCHACO Suntrail Womens Hiking Shoes Size 8 bx77Merrell Orbit Moc Size 8.5 Women's Black Suede Hiking Shoe 80858Women's nike Alvord 10 size 8.On Cloud Womens Cloudrunner Gray Running Shoes Size 6.5 (367069)Pear Izumi Womens Size 10 H3v2 Run Walk CleanedNike Women's Lunar Forever Gray Mesh Leather Running Athletic Shoes Size 10 , Men's Shoes Slippers Mens Mirak Slippers 'David' Fashionable SlippersConverse Women's Chuck Taylor All Star Satin Ox Sneaker Black/Black/White , PUMA Women's Nouli Lo Sneaker,Steel Grey/Blue,10 B(M) US , PUMA 19047801 Womens Tazon 6 Metallic Wn Sneaker Black-Grape Kiss Size 6 -NIB , New Balance WW813BK 813 Walking Athletic Comfort Sneakers Women's US 10.5ENew Nike Dual Fission Training Shoes Size 6.5adidas Adiease - Black - 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."