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.DREAM PAIRS Women's Formosa_2 Low Platform Wedges Ankle Strap Open Toe Sandals , SAS Womens Tripad Comfort Leather Burgundy/Black Cherry Penny Loafers Size 7.5 N , Salvatore Ferragamo Flats Loafers Leather Crocodile Black Womens Sz 7.5 NNew Womens Pink & Black Crocs Isabella Graphic Flip Flops, Size 11 , Ladies Shoes Cherry New Black or Grey Leather Zip Up Casual Comfort Size 6-10VANELi Womens agneta Closed Toe Mules, navy minilizp, Size 8.5 r7Ns , Klogs SONDRA Women's Clogs Black Smooth Leather Shoes Display Model 11WCLARKS 03540 MARIGOLD WOMEN'S BLACK LEATHER SLIP ON SHOES NEW IN BOXNEW MISSONI sz 5.5 JACQUARD BALLET FLATS SHOESBritish Womens Girls Literary Rhinestones Loafers Slip on Creepers Shoes CasualSz 6 New Dr. Scholl's Women's Casual Pebble Leather Shoe "Emily" Brown , WOMENS NEW BALANCE 450 TENNIS SHOES WHITE/GRAY SIZE 7Bernie Mev Charm Yael Pewter Womens Slip-On Size 41MECCO Womens Intrinsic1 Black Walking Shoes Size 7 (311165) , Mizuno Wave Legend 3 Running CrossFit Fitness Marathon Jog Shoes Women Sz 6.5 , NEW Women's Sz US 8 NIKE Pedali Combo Running Track Shoes Black/White *S13 , Women Casual Platform Wedge Hidden Wedge Shoes Low Top Walking Breathable Sbox14 , New. GIUSEPPE ZANOTTI Kevin Camoscio Suede Slippers Shoes Size 7 US 40 EU $650Men Rare Design Slip On Shoe Size 11 House Slippers Yellow Leather Pointed ToeMerrell Elephant Pink Women's Hiking Sport Athletic Shoes Size 7.5 M , Ladies Tennis Burgundy Everlast Size 8 1/2SKECHERS Bikers Engineered Knit Bungee Sneaker - Women's Size 9.5 Black , Women's Charlotte Russe-Cheetah-Women's-Beige-Flats/Shoes-Strap-Size:6 Low-priced FlatsNEW BALANCE WPACEPB WOMEN'S BLACK REFLECTING RUNNING SHOES NEW IN BOXCONVERSE ALL STAR CHUCK TAYLOR WOMENS CT HAWRDWARE HI SZ 9.5 BLACK WHITE 549630C , Sam Edelman Baylee Sneaker-Women's Size 7 Blush , ASICS GT-1000 Breast Cancer Awareness Size 6.5 Women Running Shoe Black Hot PinkNew Balance Womens Wx608hh4 Gray Running Shoes Size 8.5 (369332)New Balance Womens - Black Running Shoes Size 8.5 (352782)Cole Haan Red Women's Tennis Shoes Size: 9B ,
"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."