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.Gold Rubber Jelly Flats Made In Brazil Size 8Skechers Womens Mary Jane Flats Slip On Shoes Brown Size 6.5 M , ECCO Receptor Women's Casual Shoes Briwn Fashion Sneakers Size 40 USKEEN Cortona Women's Red Canvas Flats Bow US 10.5//New with Box , New Women's Skechers De Ja Vu Fashion Sneaker Slip On Shoes 22660 Taupe 36D , Eastland Carly Women's Leather Shoes Brown Size 7.5M , Crocs Celeste Womens Mary Janes Flats 10 Green Suede Rubber Casual Walking Shoe , Marc Fisher Women's Xena White Rose Gold Sneakers Brand New Size 6MHush Puppies VERSE Genuine Leather Slip-on Flats Shoes, 7.5N - MSRP $95 , Liendo By Seychelles Womens Ronda Ruffle Wedge Shoes Taupe Size 7.5 New , SPERRY BLUEFISH LIBERTY ART FLORAL PINK LEATHER TOPSIDERS, SIZE 7.5MNew Women's Skechers Relaxed Fit: Conversations - Holding Aces (22551) (B2) 7Kemeikell Womens 39 US Orange Leather Loafers Mocs Shoes , New Clarks Alitay Giana Black Patent Leather Slip On Flats Woman's Size 8.5 MDC skateboard sneakers sz 9 M purple leatherCamper Wabi Mens Dark Blue Wool SlippersL.B. Evans Radio Tyme II Leather Slippers, Men's Size 9, Black NEW , Brooks Ravenna 7 Running Training Women’s Size 8 US Pink Punch Gray Green , New Puma El Roo Mid Women's Shoe Boots Faux Fur US Size (6) , womans 10 white GOLF SHOES NIKE female ladys 9 low sneaker cut brush cleaner cle2018 Fashion Breathable Ladies Zip Hidden Wedge High Top Board Sneakers Shoes sz , Women's womens flat pointy Shoes Beautiful In Colour Flats , Adidas BA7545 Sonic Drive Running Training Athletic Shoes Sneakers Black Womens , 620658 101 NIKE Womens FLYKNIT LUNAR2 , Nike Free 5.0 TR Fit 4 Women's Purple Running Sneaker Sz 7 1262 , Cole Haan Women Shoes Casual Grandpro Stitchlite Sneakers NEW AuthenticNike Downshifter 6 (Wide) Women's Running Shoe 684767 002 Size 10 , New Balance Womens 7.5 M Fresh Foam Zante v3 Gray Orange Running Sneakers ShoesFoxy Denim 10" Tall High Top Sneakers Shoes Women's EU38 US5.5 Zipper , NEW REEBOK F/S HI CLASSIC WHITE/REEBOK ROYAL V56092 SIZE 8
"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."