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.Born B.O.C Black Leather Comfort Clogs Slip On Shoes ~ Sz 6 US / 36.5 Eur , Womens Blue Leather Softspots Penny Loafers Size 8 Narrow Slip OnsCole Haan Women’s Driving Loafer Brown 7 1/2 M Pre-owned , New Women Men Fashion stylish Casual Health Canvas Flat Shoes - Purple TF , SANUK Kat Paw TX Women's Red Plaid Slip On Flat Shoes Size 6 NEW , Dr Martens Womens SHOES OXFORDS Sz 7-7.5 Eur 38 Brown Cap Toe Air Wair EPOGentle Souls Women's Shoes Brown Leather Flat w Elastic .5" Heel Size 9.5M , PAUL MAYER MOODS canvas shepard country sheep trees scene print loafers shoes 9Not Rated Women's Sand City Slip On Shoes TanPrada Womens Pumps Size 37.5 Beige Black Leather Slip On Round Toe , ARRAY Womens Breeze Leather Closed Toe Ankle Strap Loafers, Beige, Size 8.5 1wyELucky Brand Maiaa Studded Bootie Almond Toe Suede leather Sz 6.5M , New Womens Skechers You Slip On Sneakers Style 14951 White/Black 117P-Q armNIKE womens free run 5.0 V2 Apple Green Turquoise Fluorescent Rare Size 8.5NEW TIPE E TACCHI WOMENS LOAFERSKUNSTO WMN 39 US BLACK LEATHER FLAT DRIVING MOCCASIN LOAFER SHOE SLIP ONCONVERSE ALLSTAR "MINNEAPOLIS" WOMENS 11 USED BABY BLUE WHITE see pics-detailsWomen's Nike Prestige 3 Skinny Hi Pink Sneakers 551649-601 Size 6 Nice Condition , Women's Nike Wmns Shoes Size 9.5 Large Assortment Athletic Shoes , WOMENS ADIDAS STAN SMITH W in colors WHITE / WHITE / SUPCOL SIZE 9.5 , New Balance Women's 1400v3 Shoes Grey with Blue 5 BNew Balance Women's Fresh Foam 1080v7 Shoes Grey with Pink & Orange 5 B , Adidas Superstar 80S Casual Women's ShoesConverse Chuck Taylor All Star Ox Barely Rose Womens Canvas Low-tops Trainers , Merrell Womens Siren Edge Waterproof Vibram Athletic Trail Hiking Shoes Size 9.5Converse CTAS Madison OX Women's Shoes Navy/Gold/White 560688C , NEW IN BOX WOMEN'S 8 9 10 VANS ISO 1.5 MESH ECLIPSE BLUE WHITE SKATE SHOESReebok BS9479 Studio Basics Track Shoe Athletic Women Shoes Size 10PUMA Women's Basket Metallic Platform Sneakers, Gold, Size 8.5 - / RX29/30 , Reebok Women's Run Supreme 2.0 Leather Womens Shoes / SIZE 10 WIDE ,
"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."