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.ATHLETECH OFF WHITE SHOES WOMENS SIZE 9 MJessica Simpson white metallic ballet flats with a black trim size 9.5 , FIONI BRAND BLACK FABRIC NWT BALLET FLATS SZ 11MWomens Merrell Apure Dark Brown Leather Loafers US 8Sperry Topsider Silver Sparkle Boat Shoes Womens Sz 8 MNINE WEST Women's Gray/Red Ballet Flats Loafers Shoes Size 7.5 M US!Women's Dansko Enya Black Slip On Suede Clog Slip Resistant US 7.5 - 8Merrell Encore Groove Brindle Womens Size 7.5 Wool/Suede Clogs Mules Slides , Sperry Top Sider SHORESIDER Women's Shoes Slip-on Sneakers, Graphite Size 6 MPUMA Womens Cell Riaze SteelGray/Drizzle/Bay Running Shoes Size 10 (367995)Clarks Narrative Hayden Opal Square Toe Loafer - Size 7 M, Black , ASICS TN875 ATHLETIC SHOES WOMENS 8.5 ATHLETIC/RUN/ CROSS TRAIN SHOES FREE SHIPNike Zoom Rival S Ladies Track Shoes (spikes) Size 8.5 Purple Yellow And BlackNike Air Zoom Odyssey Womens 9M Aqua & Orange Running Shoes GC!!! , SAUCONY COHESION 6 Women's Training Running Shoes Sneakers Size US10 UK8Skechers Shape Ups Mary Jane Womens Fitness Toning Sneaker Black Sz 9 US , Saucony Womens Fog/Red Running Shoes Size 8.5 (14447)New Womens DKNY Mule Sneaker Shoes 5.5 White Purple Metallic SilverDr. Scholl's Madison Sneaker, Women's Size 9 M, Taupe , Women's lower east side slip on Characteristical Flats , NIKE FREE TR FLYKNIT MTLC SIZE 12 WOMEN'S RUNNING CROSS TRAINING (804534 003) , Nike WOMEN'S AIR FORCE 1 Ultra Force Mid Black/Sail SIZE 6 BRAND NEWConverse Chuck Taylor CTAS 553436C Missoni Hi Multi Women's Shoes Size 8 125$NIKE WOMEN'S SZ 8.5 FREE RN MOTION FLYKNIT 2017 multi color 880846 004 NO TOPRoyal Elastics Icon 1707 White Blue Pink Leather Women Shoes Sneakers 92073-510NEW ASICS Women's Gel-Torrance Running Shoe Aluminum Bay Mid Grey Multiple SizesNike Air Max Ivo Running Shoes Pure Platinum White Blue 580519-014 Women's NEWConverse All Star Shoes Size 11 BlueSkechers 48855 Womens Lite Step Flat- Choose SZ/Color.BX704 SARA LOPEZ shoes black leather women sneakers EU ,
"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."