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.Loafers woman 37 black blue burgundy college shoes moccasin eco-leatherAnne Klein Black Alligator Flats Shoes Iflex Size 7.5 Ladies Womens New NibKLOGS Shoes Via Mary Jane Womens US size 9 Brown Beige Leather Sport FlatsWomen's Born Black Leather Heeled Loafers US 6 , CORAL BLUE BALLET FLATS 37 NEW espadrilles peeptoe sandal slipper slip-in , Franco Sarto Womens scranton Leather Pointed Toe Mules, peach su, Size 6.0 qbY6Josef Seibel Women's Eu 39 US 8 - 8.5 Brown Leather Monk Strap Comfort ShoesSperry Top-Sider sequin leopard boat shoes flats size 8 , Betsey Johnson Boom White Womens Shoes Size 9 M Fashion Sneakers MSRP $69 , Cole Haan womens brown leather slip on loafers mocassins size 7Marquiiz Women's Embellished Floral Espadrilles Flats CB4 Pink EUR:41 US:9.5$140 New IVANKA TRUMP KENNI 6 Red Multi Fabric Designer COMFORT Casual Flats 9.5 , Love by Ellen Degeneres Tennis Shoes - Atala sz. 9.5 Grey , Women's New Balance 643 Shoes Sneakers Sz 9B Brown Blue Hiking Trail Outdoor B15FRICOTE Tennis Montantes Daim Orange Clair T 41 TBEMojari Women Shoes Leather Khussa Indian Handmade Ballet Flats US 5.5-8.5Cool Funky Women Ladies Canvas Shoes Comfort Lightweight Flat Casual SneakersJessica Simpson Womens Fusto Low Top Slip On Fashion Black Heather Size 7.5 lNWomen's PINK CONVERSE SNEAKERS SIZE 6 Genuine Athletic Shoes , ?NEW Women's NIKE COURT LITE Purple Tennis Trainers 845048 651 Size 6.5, 10NIKE AIR MAX 90 ULTRA MOIRE WHITE RED RUNNING WMNS SZ 6.5 - 9 * 704995-102 *Puma Suede Mid Winter Elemental Fashion Sneaker Women's Shoes Size 6 , Rieker R3402 Liv 02 Perforated Leather Sneakers, Women's - Size 8.5-9, GreyWomens Nike Lunar Summer Lite 2 Golf Shoes 13R , Reebok Women's Vintage 1990's OG Walk Ultra DMX Shoe 11-51281 Black sz. 8.5Skechers 15600W Performance Womens Go Joy Walking Shoe- Choose SZ/Color. , Skechers Performance 14941 Womens Go Outdoors- Walking Shoe- Choose SZ/Color.Puma Womens Size 10 Suede Remaster Blavk Casual Sneakers ShoesConverse Chuck Taylor made in USA sneakers size on bottom is 2.5 new without boxWomen High Top White Shoes Flats Breathable Suede Pull On Zsell
"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."