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.Cole Haan Women’s Blue Loafers 9 , MERRELL Oceania Black Women's Size 8.5 Leather Slip On Flats Shoes Vibram SoleNot Rated Womens Pinka Black Leather Oxfords Shoes 8 Medium (B,M) BHFO 5030NICOLE " SNIP " LEATHER SHOES SIZE 10 WHITE RED SNAP DECORATION FLATS SLIP ONSClark Indigo Womens Strap Comfort Pumps, Size 11MWomens Minnetonka Brown Leather Moccasins Size 8 Fringe Trim Cushioned Footbed , Dansko Womens Olivia Claret Floral Leather Flat - Purple Size US 7.5-8Nine West Womens Lightning Leather Pointed Toe Loafers Natural Size 10.0 LC1q , COLE HAAN Black Woven Leather Slip on Loafers/Flats ~ 7.5B ~ Nice ~Made in Italy , Gianni Bini Flats 8 Shoes Suede Rhinestone Leather Slip On Cut Out Womens SizeHardy NAOMI Round Toe Loafer, Women's Size 7.5, BlackKlogs Women's Clogs Display Model Shoes Salma Black KPR 8.5 MVince Warner Blue Womens Shoes Size 7.5 M Flats MSRP $225Women's Sneakers Sport Running Shoes Training Outdoor Casual Walking Mesh Comfy , 2019 New Womens Winter Vogue Square Toe Low Heels Loafers Sweet Lolita Shoe T570Trotters Womens sizzle Closed Toe Ballet Flats Navy Size 9.5 8PLE , New Womens Adidas Ambition Track and Field Cleats/Shoes 8 12 Pink/PurpleSaucony NX Running Shoes 8.5 Silver BlueForever Collectibles NFL Dallas Cowboys Moccasins Open Back Tan Slippers NewWomen's ASICS Gel Kayano 21 Running Shoes Sz 7 Purple Grey Neon Green T4H7NPropet size 9M Washable Walker brown bronze walking womens tennis shoes W3840Nike Zoom Fit Agility Athletic Running Sneakers - Turquoise/Pink - Size 8 (US) , Women's NEW STEVE MADDEN WOMENS ZOVA Practical And Economical Athletic Shoes , Women's Fergalicious Women's Addison Ballet Flat Superior In Quality FlatsWomen's Black Flats with Roses Diversified In Packaging Flats , Skechers Shape Ups Women White Leather Walking Shoes Size 7.5IPPON VINTAGE Run Silver Pailleté Argent , Steve Madden Glacier Sneaker, Women's Size 7 B, Black , Asics Gel Kayano 21 Size 9.5 Women's Running Shoes Turquise Neon Coral T4H7NAVIA WOMENS ATHLETIC SHOES SIZE 9.5 MEMORY FOAM WHITE PINK LADIES CASUAL STYLISH ,
"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."