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.NEW BEBE SUSANN SHINE BALLET flats SIZE 5 Shoes COMFORTABLE TOES SHOES , WHITE MOUNTAIN LEATHER WOMEN BOOTIE-ZIPPER W/2"HEELS BLACK-SIZE 9.5-W-NEW IN BOXCLARKS UNSTRUCTURED Brown Leather Loafer Moc WOMENS 6 M ShoesCOLE HAAN Women's Black Patent Leather Fashion Flats Shoe Size 9.5Hotter Comfort Concept Women's Mary Jane Mauve Pink Leather Shoe Size 5.5Women's Dansko Madigan Vegan Mules Clogs Shoes 36 / 5.5 / 6 , SoftWalk Women's Chatsworth Mary Jane Flat, Sage, Size 7.5circus caley rose shadow shoes 10 m by Sam Edelman new in Box suede flat shoes , NEW ECCO Strap Comfort Loafers Brown Leather Walking Shoes Cute! 38 7-7.5 , Sesto Meucci New 8 N Narrow Brown Leather Flats Basketweave ItalyCole Haan "Pinch" Burgundy Suede Leather Weekender Loafers Women's 9M/New /$100Dr. Scholl's Womens Joliet Closed Toe Slide Flats , Women s Outdoor Sports Shoes Fashion Breathable Casual Sneakers Running Shoes 8H , Adidas Superstar Pearl Grey/Icey Pink Men's Size 7 Pre-Owned , L Orchid Ladies Flat Heels Loafers Rivet Decor Slip on Shoes Court Grace SandalsSkechers Performance Women's Go Walk Lite-15412 Loafer FlatBlack/Gray8.5 M USNike Lunarswift 2 Women's 7 White/Black/Tan Running Training Walking Shoe , Salomon Ellipse Women's Thyme Hiking Shoe 6MBrooks Adrenaline GTS8 Women Size 6.5 D Athletic Running Shoes Blue/Silver *MintNative Womens Apollo Moc Pink Casual Shoes Sneakers 9 Medium (B,M) BHFO 9291Women Converse Chuck Taylor Dainty Metallic Leather Low Top, 553336C Sizes 6-10Skechers Women's Bikers-Crossroads Fashion SneakerBlack8.5 M US , New Under Armour Women's Micro G Assert 7 Running Shoes Size 12 Graphite / BlueNike Women's Dual Fusion Run 3 NEW AUTHENTIC Grey/ Black/ Pink 653594-012Skechers Sport Women's Breathe Easy Nice N Cool Sneaker - Choose SZ/ColorWomen's New Balance Fresh Foam Zante Runners (W1980PB) - Purple/Multi-color , Vans Old Skool (Gold Eyelets) Grey Ridge- Women's 9 , Ryka Women's Sky Bolt Black/Grey/Mint Walking Sneakers ShoesGradient Green Print Knitting Shoes Spring Outing Slip On Loafers Casual Sneaker , Keds Champion Oxford Black/Black Canvas Women's Sneaker WF24700 ,
"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."