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.Report Women's Brown/Pink Leather Peep Toe Perforated Ballet Flats Sz /US 8PRE JBU by Jambu Women's Wildflower Too Mary Jane Flat RED PICK SIZE 8 , Shellys London Womens Abeniel Canvas Round Toe Loafers, Gray, Size 9.0 W5UIZinc Embroidered Bow Ballet Flat Shoes Slip On Leather Suede Textured Sz 7 RARE! , Ecco 36 Loafer Black Leather Slip On Comfort Career Work 5.5 Casual Basic Shoe , ANGEL STEPS WOMAN'S SHOES TAUPE Straps Comfort WALKING SHOES SIZE 7Rampage Women's Delila Comfortable Flat Fashion Great for Work LoaferMerrell Moc Women's Brown Comfort, Slip On Size 9 (B12) , Wilady Women's Nasty Gal Holographic Flatform Trainer Sneakers TW4 Navy US:6Ferragamo Salvatore Pump Heels Shoes~ 7.5 , Merrell Boulder Shoes Women's Sz 7 Brown Slip On Leather Upper Performance Sole , Marc Fisher Womens Dezie Suede Low Top Slip On Fashion Sneakers, Pink, Size 6.0 , Z58 Eileen Fisher Oath Earth Nubuck Leather Weaved Sneakers Women's Sz 11 M , Merrell Q Form Air Cushion Hiking Walking Shoes Sneaker Women's 6.5 , Vintage VERSANI Black D'orsay perforated Heels 8.5 Gold studded Excellent Italy , Walking Cradles Women's Feather Boot, Black, 7 M USARRAY Womens Freedom Leather Square Toe Loafers White Size 7.0 S1KK , Joan & David Handmade Shoe Woman Italian Worn SZ 71/2 Alligator Design RARE VTGNew! Women's Skechers 12140 Soleus Athletic Shoes Black I65 , Bobs Skechers Women's B-Loved Denim Sneakers Sz 7New Balance Women's Size 6.5 WX20SG6 Orange Athletic Minimalist Shoes ZV-805 , Women's ladies flat shoes size 9 Reliable Performance Flats , nike Air Huarache Run CROC Print OBSIDIAN NAVY US WOMENS SHOE SIZES 725076-401 , $160 Vivobarefoot Womens Linx Mesh Golf Shoes, Chocolate/White, 39 EU / US 8 , Vasque Womens Talus Mid UltraDry Leather Athletic Hiking Shoes Sz 7.5 WideAsics Gel Nimbus 19 Women's Athletic Running Shoes T750N Carbon Flash Coral SZ 7 , Nike Volley Zoom Hyperspike 585763-016 Black Pink Volleyball ShoesWomens Size 15New Nike Womens Air Max Sequent 2 Platinum White Grey Running Shoes sz 9Saucony Triumph Everun ISO Women’s US 6 Running Shoes Turquoise Purple EUCKeds Men's Champion Original Canvas Sneaker - Choose SZ/Color
"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."