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.V38 Paul Green Kianna Black Patent Penny Loafers Shoes Women Size US 9.5 MUNIONBAY Women's Demi-u Ballet Flat, Black, 8 M US , Wear. Ever. Temika Woven Slip On Shoes, Women's Size 10M, BlackBorn Brown Genuine Leather Slip-on Loafers Women's Size 8Clarks Artisan Red Leather US 8M SlidesWomen’s Bean Boots By L.L. Bean Shoes Boots 9 M Made In The USA , Ladies Casual Pearls Slip On Loafers Pointy toe Shoes British Style Court Shoes , Spring canvas breathable ladies wild sneakers running leisure high shoes , COLE HAAN AIR KAYDEN OXFORD SHOES WOMEN'S 10.5 B NIBCole Haan Women’s Cortland Ballet Flats Slate Cap Toe Shoes 6.5 , Josef Seibel Carole 6.5 Brown Mule Women's , Cobbie Cuddlers Women's Tan Emery Sneakers Shoes Sz 6.5 Medium , Womens Saucony Excursion TR10 Gray Trainers Size 8M (X420) , Nike In-Season TR 4 Women US 9.5 Cross Training Running Shoes 653543-001 J8Saucony Shadown Original Sneaker - Women's Size 8 RedDEXTER SLIDE-RITE Women Bowling Shoes Size US 9 M Black LeatherDiadora Women's Kuruka W Running Shoe, Pink Fluorescent, 6.5 M US , Brooks Ghost 7 Womens Running Shoes Sneakers Sz 8 M Pink Black , Women's BASKETS "Palladium" New Style Athletic ShoesWomen's Bebe Dane Women's FLATS Navy Modern Techniques Flats , Reebok Size 9 Pink Light Weight Sneakers New Womens ShoesNIKE SAMPLE AIR MAX THEA JCRD (JACQUARD) SZ: WMNS 7 (654170 500)Steve Madden Decaf Black Fashion Sneakers Women's Size 6 M*Easy Spirit Romy Light Pink Womens Sneakers Size 6MNew Balance Q117 520 V3 Running Sneaker W520RL3 Size 6.5 , American Water Spaniel Running Shoes For Women-Free ShippingAdidas Running Shoes Womens 7 Incision? Trail Black Pink C145Skechers Women’s Black Shape Ups Fitness Walking Sneaker/Shoe Size 7.5 $250Brooks Womens 1202471B057 Silver/Grey/Rose Walking Shoes Size 9 (30731) , WMNS REEBOK CL LTHR 49801 WHITE/GUM DEADSTOCK BRAND NEW
"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."