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.Free People Women's SZ US 8 Black Suede Slip On Ballet Flats Studded S181LUICHINY "VAY KAY" SLIP ON SHOES LADIES US 5.5 med NEWWomens Earth Shoe Size 8.5 Brown Leather Mule Slip On Wooden Heels , Vince Camuto Brown Leather Sandals Flats Flip Flop Slip On Shoes Size 8B 38FADED GLORY Women's Surfer Moccasin Casual Slip On Shoes canvas gray flats 6New Womens Ankle Strap Pumps Flats Ladies Bow Ballerina Strappy Dolly Shoes , BELLOFATTO Glitter Flats Size 9.5 B Shoes Made In Italy Dark Silver Shine , BOC Born Womens Clogs Sz 10/42 Med Black Leather Paisley Casual Career LoaferCrocs Everleigh Summer Sandals Pink Flats - Women 10 , 11Born Women's Shoes Penny Loafers Suede two-toned Brown 8 (C48) , Lands End Tan Suede Leather Slip On Loafers Shoes Comfort Women’s Sz 11 B , Eastland Women's 9 M Brown Leather Split Toe Slip On Tassel Loafer Shoes Clogs , Alegria "Pesca" Blue Veg Fisherman sandals 39 (US 8.5-9) PES-630 GUC , Womens 8 M Born Mount II Clogs Shoes Black Leather Slip-On Comfort Mules SandalsComfort Plus by Predictions Women's Size 11W Black Loafer Shoes Excellent , ELITES by WALKING CRADLE Womens ALEX Sage Urban Leather Clogs Size US 11 M , Women's Minnetonka Kilty Suede Moccasins - 401T - Grey - New in Box! , Carlos by Carlos Santana Womens malinda Low Top Slip On Fashion White Size 8.0Women's Eeric Javits Squishee Moc Loafer Hickory/Black Braided Fiber Size 7 M , Jump Women's Gloom Flats Ivory Leather Size 5.5 MSANUK Fiona Women's Charcoal Sidewalk Surfer Slip On Flat Shoes Size 6 NEWJ Lo Silver White Platform Sneakers 8 , Ecco Biom Women Shoes Gray Slip On Mary Jane Loafers Sport Walking Sandals Sz 42Newton Running MV2 - Black - WomensWomen's Floral Flats 6.5 Special Buy FlatsKids Nike zoom pegasus 34 gs turchese size 6y runnung shoes 881954 300 , Nike Womens Air Zoom Pegasus 34 Athletic Snickers Running Training Sz US 5.5Saucony Womens Zealot Iso 2 running Shoe- Pick SZ/Color.Fitflop F-Sporty Mirror Toe Black SneakersPuma 187351 09 Cell Riaze Heather Gray Aqua Green Women's Athletic Shoe Sz 9.5
"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."