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.Croft & Barrow Ballet Flat Shoes Blue Women’s Sz. 9New Korean Women's Sneakers heels Leather Platform Breathable Casual Shoes PD3URBAN OUTFITTERS SUZI BALLET FLATS SHOES SIZE 8 100% SUEDE LEATHER NIOB , 388 COLDWATER CREEK women's 8 M BROWN LEATHER mule moccasin shoes Flats Slides , AIS Women's White & Pink Skull Heads Shoes Size 3 *NEW*� Clarks Privo Mary Jane Ballet Flats size 8.5 M Olive & Brown Leather & Suede , ARRAY Womens Freedom Leather Square Toe Loafers, Beige, Size 10.5 gn8V , Sperry Sayel Dive Palm Sky Sneaker, Women's Size 6.5, BrownLadies Black Shoes Flats Size 8 Medium , New Santoni Italy Tan & Light Gold Cotton Canvas Venetian Loafer 7 BCOLE HAAN Olive Green Suede Driving Shoes Loafers 9.5Adult Women 2" Pf Monk Creeper D Shaped Buckle Shoes Flats , Skechers Bobs Sport Squad-Awesome Sauce Gray/Aqua Womens Sneakers Size 9M , New J/slides petwer leather aztec shoes. SZ6.5. RT$135.Olukai Momi Shoe - Women's Coral / Coral Size 7 , Aerosoles Good Times Dress Flats, Black SuedeReebok Black Pink Mesh Running Athletic Sneaker Size 8 , Ros hommerson champagne pewter metallic oxford leather Nelly 12 narrowEasy Spirit Tunein Light Pink Womens Slip-On Size 6.5M , Skechers Womens - Black Walking Shoes Size 10 (364594)ARAVON by New Balance LEATHER Athletic Sneakers Casual SHOES Womens Sz 8 AA ??Women's NIKE Flyknit Zoom Sneakers Size 8.5Women's Women's wide width shoes New Product FlatsSaucony Freedom ISO 2 Black Running Shoes Women's US 8 (I2,12) , Reebok Princess S WHT/ANT ROSE Vintage Sneakers New Old Stock with Box , New Nike AIR FORCE 1 HI PRM SUEDE 845065-600 Wmn Noble Red/Black-Plum Fog Lthr , Skechers Breathe Easy Big Bucks Sneaker - Women's Size 11 Black , Nike Huarache Run GS Kids Youth Womens Running Shoes Lifestyle Sneakers Pick 1 , Keds Women's Kickstart Metallic Linen SneakerRocket Dog Junglegym Women's Causal Pumps Plimsols Fashion Trainers Pink
"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."