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.Naturalizer Wedges Mules Closed Toe Womens Brown Leather Slip On Shoes 6.5M NWOB , Update L4916 LadiesTurquoise Slip On ShoesBorn "Toby" Black Metallic Snake Print Leather Fashion Clog Sz 9 40.5Steve Madden Womens Emilie Leather Pointed Toe Ankle Wrap, Blush Suede, Size 8.0 , CUSHE WOMEN'S CHARCOAL METALLIC BALLET FLATS - NWOB!!! FREE SHIPPING! NEW!!!Soft Style By Hush Puppies Dee Heels - Women's Size 9 EW, BordeauxNew Betsey Johnson Coco Dazzling Flats. Sz 6 M. $ 99Women's Sperry Top-Sider Intrepid Dark Grey Silver Boat Shoe Size 8Sperry Womens Burgundy Size 7.5 M Top Sider Angelfish Leather Boat Shoes LoafersLadies Leather Shoes Cherry List Full Leather Mary Jane Style Size 5-10 , Womens SAS "EASIER" Antique Wine Burgundy Leather Loafers Shoes SIZE 8 Narrow , PINK FLOYD CONVERSE Rare Ed. High Top Shoe 1987 Wish You Were Here Womens Size 6 , 345 Joie Huxley Gray Suede Cutout Slip On Sneakers Women's Sz 36 M , Handmade Elephant Rope Women's Sandals - Sizes 4-10 US W80% off NEW MUNRO AMERICAN Journey Shoe Black Nubuck az 7 Extra Narrow $184 , L.L. Bean Tan Brown Hiking Shoes - Women's 8 1/2 MH3 Clarks Mens Indoor Outdoor Slippers Size 11 US brown house shoesVans Off the Wall Shoes Lavender Women Sz 7.5/Men Sz 6 NWOBWomens Nike Reax multi color running shoes sz 9.5Women's Asics Gel- Venture 4 Running Shoes Purple Gray Sz 9 GUC , BABOLAT Propulse Team Women's Size 8 Tennis Shoes White / Pink/ Aqua , ASICS Women's GEL-Flux Running Shoe Sneakers Size 9.5 Blue Pink WhiteNew keds sneaker mules ladies athletic shoes size 7 canvas open back , New Womens Ladies 6.5 Under Armour UA Horizon Trail Running Shoes , Isabel Marant Womens Gray Beige Suede High Top Fashion Sneakers Size 40 10New Authentic Puma Muse Echo Shoe Puma Black Silver 36644703 003 Women sz 9.5NEW IN BOX WOMEN'S 10 VANS SK8-HI SLIM CASTLEROCK BLANC DE BLANC SKATE SHOESWomens Nike Blazer Golf Shoes Solar Red Pink White Black SZ ( 818730-601 )Skechers Performance Go Run 400 Sneaker - Women's Size 8 Gray , NEW VANS AUTHENTIC SLIM JERSEY SMOKE WHITE SHOES WOMENS 10 MENS 8.5 new ,
"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."