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.Lauren Ralph Lauren Abigale Flats 789, Black, 8 US / 38.5 EU , Jessica Simpson Mariza Women's Sandbar Flat 6.5M , LAND'S END sand suede Butterfly front flats shoes sz 8M , Women's Alegria Dayna Mary Jane Shoes Size 38 (US 8 - 8.5) Black Napa DAY 601Ballasox New with Box Festive Blue Size 6 Teal/Butterskin/ Stretch Lycra s17832 , Maraolo For Neiman MarcusShoes Women’s Vtg.80's mesh and leather flat Size 7 , Vaneli Shoes 6 M Loafers Leather Womans BrownKeen Black Mary Jane Size 10 Slip Resistant Style 5368Ballerines kaki et sequins dorés T 38 , Designer Liz Claiborne Black Comfort Slide LC Ashton Raise Dress Loafers 8.5 M , Clarks Unstructured Womens Brown Leather Comfortable Mary Janes EUC SZ 6.5MLIZ LISA - Enamel ballet shoes ( Japan kawaii lolita harajuku)PAUL GREEN BLACK LEATHER DRIVING LOAFER SHOES US 11.5 AU 9 , Women's DANSKO "Marcelle" Black Patent Leather Mary Jane Shoes 41 (10.5 US) , Skechers Pure Street Running Shoes, Grey/Pink/White, Women's US 7.5 , Womens Mizuno Wave Creation 14 Running Training shoes size 11 US , VANS. Women's or Men's CAMRYN Tan Casual Canvas HI Shoes. Womens US 10.5.Copper Fit Women's Merry Mesh Slip on Shoe Sneaker Pink /Peach 9.5 MNike Women's Size 6.5 Kaishi Winter High Sneakerboots BLACK 807195-001 nwbox , Merrell Ridgepass Hiking Trail Shoes Expresso / Blushing / US 8.5 , ASICS Women's fuzeX Rush Running Shoe Diva Indigo Blue White 6.5 M US WORN ONCEWomen New Balance WL005PM Sneaker Shoes Medium (B) Pale Grey 100% Original New , Women's Adidas UltimaMotion - Carbon/Carbon/Core Black - Width: med - RunningWOMEN'S New Balance? W790 Size 9 Running Shoes Mint/Pink/Navy , Women Leather Round Toe Fashion Sneaker Flat Heel Sport Ankle Boots Oxfords PunkNew Balance Womens - Black Walking Shoes Size 7 (368530) , K-Swiss Lozan III women's sneaker shoes trainersReebok RECORD MILE CLASSIC WOMEN Rivet Gray/White/Luster Pink Sneakers size 6 , Altra A2634-3 Torin 2.5 Running Training Wedge Purple Sneakers Women's US 11 , Skechers Womens Go Train City Assert Cross Training Black/White 7 B(M) 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."