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.Flexation Falco by Aerosoles Womens Brown Leather Wedge Loafer Shoe - Size 9.5M , CROFT & BARROW Women's Off-White Light Beige Ivory Leather Flats Shoes SZ 6.5Men Women Canvas Flat Slip On Casual Shoes Sneaker DIY Hand Painted Shoes , SAS Tripad Comfort Beige Leather Loafers Womens Size 8S , L.L. Bean Women's Comfort Mary Janes Shoes Size 11 Medium Leather Brown , NINE WEST Women's Chocolate Brown Leather Fabric Flat Slip On Shoe Size 11MDansko Women Size 42/ US 11.5-12 Brown Leather Shoes,(#D08)Rialto Sunshine Bow Ballet Flats, Black, 10 US , Giani Bernini Women's Jonnie Stretch Flats Pewter Ice Leather Size 7.5Women's Taos Applause Loafers Shoes Size 7B Mary Jane Black Leather Strapped AB8INC International Concepts Elsah Women's FLATS Black , EASY STEPS KENT SIZE 11C (AUS)Skechers Shape Ups Womens 9 M White Silver Toning Athletic Walking Shoes 11814 , Easy Street Women's Effie Flat, Navy, 12 M USMunro American Jewel Comfort Womens Athletic Shoes Sz 8 N Mocha $220WOMENS CATAPULT CONQUER ULTRA LITE RUNNING SHOES US 10KangaRoos Gray Pink Zipper Pocket US Size 9.5 Sneakers Shoes Jogging , Adidas Adiprene Women Running Athletic Gym Sneakers Turquoise & Gray Sz 10 , Skechers Performance Go Walk 4 Exceed Slip On - Women's Size 7M BlackU.S. Polo Assn. Womens Yvonne Winter Boot WP Black Size 6 M US , Women's Zumba shoes size 10 High Quality Athletic Shoes , Women's Naturalizer Women’s shoes size 6M Fashionable Patterns Flats , A608 Nike Women’s Air Max 90 Sacai 804550-440 Obsidian Size 7.5 New Retail $150 , NEW NIKE AIR MAX 1 ULTRA SE SHOES WOMEN'S LIGHT BONE ROSE GOLD COPPER SIZE 8 , Salomon X Ultra 2 GTX W Shoes - Women's Size 10 - Dark Teal , NEW Nike Women's Air Relentless 4 Running ShoeS SIZE 9.5 , MBT Tan Beige Leather Adjustable Strap Walking Toning Sneaker Womens 7.5Salomon Women Pink Purple WSR XR Mission 1 Trail Running Hiking Shoes 10 EUC , Nike Air Max 1 Ultra Premium Jacquard ‘Metallic Silver’ size 8 , Navy GO Run 600 Skechers shoes trainer Gym Women Sport mesh Comfort Casual 15071
"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."