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 liz & co julie black glitter pointed toe flats shoes size 8� Sperry Top-Sider Boat Shoes size 8 M Tan Leather w/ Tan Textured Accents , Keds Women's Seersucker Tan Sneaker SZ 6.5SPERRY Top Sider Gold Cup Liberty women wedge ankle boot taupe suede leatherVolatile Womens Size 6.5 M Black & White Zebra Leather Upper Loafers Shoes , Cole Haan NikeAir Suede Heels Pumps Shoes Sz 6 B Brown Womens 1A1 , Women's Dansko Sz 38 Black Slip On Shoes. WS78Columbia 1719201 Womens Vulc N Vent Slip Outdoor Uniform Dress Shoe US 8 WhiteVivienne Westwood Melissa Black And Gold Bow Flats EUCMUNRO WOMEN'S MARY JANE US 12 M M BLACK LEATHER EXCELLENT SHOESAldo beautiful navy blue oxford flats loafers Gold Accent Front Size 6.5 , COUNTRY ROAD Brand Black Leather Ballet Flats Shoes Size 38 NEW , Sperry Top-Sider A/O 2 Eye Boat Shoes, Women's Size 6 M, Linen/Oat , Womens Fashion Running Sneakers Casual Athletic Breathable Walk Sports Shoes , Women's adidas running shoes size 8 .5 - pink white metallic , CROCS Mercy Work Women's Black Gold Roomy Fit Clog Shoes Size 12 NEW , Franco Sarto Womens CENTARA Leather Cap Toe Ballet Flats, Black, Size 6.5 , Vibram Five Fingers Barefoot Running Purple / Orange Shoes Sz 38 / US 7 - 7.5Steve Madden Mens Psailor Black/Multi Moccasin Slippers Size 11 (32203) , Crocs Pink And Grey 8 Womens Two Left Shoe , New Balance Women's W1260SB4 Silver/Blue Running Shoe 8.5B , New Balance Womens 8 M WW565TN Everlight Walking Athletic Zip Shoe Beige LeatherBella Vita Womens Switch II Low Top Slip On Walking Shoes Blush Snake Size 9.0PUMA Womens 35892722 PumaWhite-pumaWhite Cheerleading Shoes Size 9 (362324) , Rose Gold Converse customised with stunning crystals All Size 4 , UBIQ x Asics Gel Lyte V "Midnight Bloom" H42BK-9951 Womens Sz 8, Mens 6 1/2 , Xtratuf Women's Yellowtail Royal Blue/Grey Size 9 Slip On ShoesNew Balance Women’s size 12 Running Shoes Silver White Green 1540SG2 Med Width , Merrell Women's Capra Waterproof Hiking Shoe - Size 9.5, TaupeWanted Shoes Women's Gramercy Fashion Sneaker,Burgundy Size 6M US
"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."