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.Women's size Black Leather Casual/ Dress Comfy Flat Slip On Shoes , Women Flats Slip On Casual Women Loafers Shoes BreathableC0033 Clarks Privo Womens Mary Jane Mint Green Black Loafers Comfort Shoes 7 M , Johnston & Murphy Melody Cap White Beige Flats Women's Shoes Size 8.5 78-11518 , Clarks Ashland Women Flat (6M, Black)Karen Scott Womens Ronni Closed Toe Ballet Flats, Navy, Size 7.0 bOVeWomen's Ecco Beige Leather Casual Fashion Sneakers Shoes Size (F12)Soludos - Women's Velvet Llama Sneaker - Navy , Raffia shoes hand woven natural raffia slides with leather sole hand woven rafiaWeejuns London Cognac Tan Leather Used Great Shape Women's 9.5 M Leather , LifeStride Women's Dig Flat, Black Kylie, 10 M USNike Air Force 1 07 Women's White Basketball Shoes 315115-112 , Drew Active Taupe Calfskin Diabetic Women's Walking Shoes 10910-72 , Dansko Black Leather Clog/Mules Open Back Womens Shoes Size 38Barbara Bui Shoes Women Brown Round Toe Bow Elastic Ballet Flat Eu 37 Size 6TS shoes TAKING SHAPE sz 8 / 39 Electra Block Heels comfy chic easy-wear NIB!Ryka Revere Walking Shoe - Women's Size 11M NavyConverse Chuck Taylor All Star Animal Hi Womens Trainers Black Sheep 500043 D41New Balance 578 Classic Women's Athletic Shoes Size 8B (W578GCS)New Levis Hi Top Black Denim Canvas And Leather Shoes for Women, Size 6.5 , MERRELL SIMPLE BALLET Women’s SHOE Size 8 TAN NUDE CANVAS FREE SH , New Bella Vita Womens Emilie Black Fashion Shoes Size 7.5 (C,D,W)Women's Skechers Taille 36 Rosebloom Neuves Discount FlatsNew Gola Active Evolve Black/Charcoal Womens Trainers ALL SIZES , New Puma 364092 01 Basket Platform VR Olive Night Women's Casual Shoes 8.5 US , Nike Air Max Thea Ultra Flyknit Women Grey/White Running Shoe 881175-002 All Szs , EUC Altra Olympus 1.5 Women's US 7 Running Marathon Jogging Zero Drop Shoes A7 , Women's Nike Air Max 1 SUMMIT WHITE RACER BLUE 704995-100 sz 7.5 RUNNING SHOESNIKE SON OF FORCE WOMEN'S SHOES ASST SIZES NEW IN BOX 616302 112 , Merrell Women's Capra Low Leather/Mesh Winterized Hiking Shoe, Granite J32462
"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."