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.Columbia Women's Vulc N Vent Bombie Casual Shoe, Purple Dahlia/Zour, 11 B USVince Camuto Women's Disti Bitter Sweet Grapefruit Ballet Flat 9M , Used Men's BOC/Born brown slip on size 12Dexter Shoes Gray Suede Slip On Womens Size 6M , Betula by Birkenstock BOSTON Taupe Tan Suede Leather Slides Clog Mule L10 M8 , **Nine West Big Apple Flats - Women's Size 9M, Black GlitterGrace womens stylish faux suede pointy toe strappy Zip back Flat Casual Shoes SzCole Haan Beige White Suede String Up Loafer Flats Size 10 B , Steve Madden Women's Lancer Fashion Sneaker, Black, Size 10.0 VsFd , LOGO Black Leather Asymmetric Colorblock Marcia Loafer 8 SALE Lori Goldstein , Revel Womens Shoes $29 BRonze STELLA FRANKIE SLIP ON SNEAKERS NEW SIZE 7 , Calvin Klein Leather Women’s Shows Flats Loafers White. Size 8 , Gentle Souls Womens Bless Word Peep Toe Sandal Flat Shoe Size 6.5 MNaturalizer Rusher N5 Booties Womens Chunk Heel Brown Leather Shoes Size 9N , Womens Tangerine Orange SPERRY Canvas Boat Shoes MINT - 9.5M , EEUC Women Skechers Leather Shape Ups Fitness Silver Shoes SIZE US 7Nike Free RN Motion FK OC 843434 999 USA ?? USA ????SZ 6.5 SAVE HERE , BROOKS Glycerin 10 Women Sz US 8 Eu 39 Running Shoes Sneakers Green Gray 42-9 , ASICS GEL EXCITE 3 Womens Running Walking Shoes Sneakers T5B9N Silver Pink US 11 , New Balance 536 Walking Shoes Women Size 10 Slip On Dual Comfort , Women's Ryka Divine Black/Pink Training Shoes Online Sale Athletic Shoes , Skechers You Define - Perfection Navy/ Gray Womens Sporty Walking Shoes Size 8MKeen Women's Hiking Shoes Brown / Mineral Blue - 8.5 (Eight and a Half) WalkingBrooks Womens Addiction 10 Shoes Size 8.5 W Gray Athletic Running , ADIDAS Pure Boost 2.0 Running Sneaker Grey White Sneaker Women's Size 9.5BROOKS PURE CADENCE 2 WOMEN'S RUNNING TRAINING SHOES SIZE 10 TEAL 120134 , Skechers 976 Street Womens Hi-Lite-Satin Canvas Sneaker- Choose SZ/Color.NEW adidas Performance BY8886 Womens Nemeziz 17.4 FG W Soccer-Shoes Size 9.5Nike Womens Tennis Classic Print Black Tennis Shoes 5 Medium (B,M) BHFO 5086 , Skechers Shape Up Sneakers Shoes Women’s 10M Leather Athletic Walking Gray Blue
"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."