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.Lucky Brand Women's Clogs Shoes Brown SZ 8M Suede Leather PACE LOVE Boho WedgeBlack/White/Gray Plaid Women's Flats (Size 8) , Women New Ballerina Ballet Flat Sexy Comfort Soft Slip On Dance Shoes Sz 6-11 , Bullboxer Wms Cute Tan Leather Shoes 7EARTH SPIRIT Gold Medallion Sandals Clogs Loafers Womens Shoes Sz 11 Leather � , BORN “Carri” Snake Skin Embossed Cork Slip On Balle Flats With Bow Comfort 6.5 M , Women’s Alex Marie Bronze Metallic Leather Flats Size 8 Slip On $89 , WOMEN'S SPERRY TOP SIDER LEATHER BALLET FLATS SIZE 7 MCole Haan 'Hadley' black suede W01054 skimmer pointed toe flats 7.5B 4818Umberto raffini US 7 to 7.5 Black Mary Jane FlatsWomens Barbour Seaside Beach Sandal Lightweight Beach Toe Post Flip Flops , Tods women's classic loafer, made in Italy , DONALD J PLINER 9M Women's GRISEL Slip On Peep Toe Perforated Ballet Flats ShoesWomen's Merrell black leather clogs size 7 - so comfortable!Chic Womens High Top Shoes Rhinestone Hidden Heel Snakers Fashion ShoesReebok Memory Foam Tech Running Shoes Womens Size 10 Gray Teal-5328RYKA "TEANNA" White ATHLETIC SHOES LADIES US 11 med NEWMerrell Womens Bare Access Arc 4 Vibram Athletic Trail Running Shoes Size 8.5**Sperry Seaside Perforated Slip On Sneaker - Women's Size 7M, RoseNew Women's Puma Fierce Core - 188977-12 - Black Silver Training SneakerSkechers Street Women's Prima-Bow Insted Leather SneakerWhite/Pink10 M US , Nike Womens Air Max Sequent 2 852465-003 Gray Salmon Knit Running Shoes Size 9 , Brooks Ghost 9 Women's Black Purple Blue Sneakers Shoes 1202252A092 Size 10.5 MGola White / Blue Tiebreak Sneakers NWBNew Balance Womens WC696WT3 Tennis Size SZ 8.5 B , Vans Old Skool Sherpa Turtledove White Women's 10 Skate Shoes New Faux FurNew Balance Women's 247 Classic Shoes Green with White , Nike Flex Fury 2 Athletic Shoes - Women's Size 9.5, Grey/Mint Green , Skechers Performance Womens Go Vulc 2- Walking Shoe- Pick SZ/Color.Katy Perry Womens the heart sneaker Leather Low Top Slip On White Size 5.0 zjY ,
"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."