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 Zara Woman Black Gold Detail Slip On Loafers Size US 7.5 /NWOB A86 , NATURAL SPORT CRADLE BLACK LEATHER FLAT OXFORDS SIZE 7 N MADE IN BRAZIL EUC , Naturalizer N5 Comfort Violette Leather Ballet Flats Sz 7 M Copper Square Toe , Seven 7 Cape Verde Flat Espadrille Women’s Size 8 , El Naturalista Frog Shock Leather Multicolor Slip On Shoes Women's 38 7.5 Brown , Libby Edelman Flats Lenora Moccasins Womens Size 8.5 Shoes White/Gold Metallic , Naturalizer ADAIR Brown Checked Fabric & Faux Patent Leather Ballet Flats Sz 6 M , New Bueno Usak Womens Leather Shoes Made In TurkeyEasy Spirit Ikatta Slip On Shoes - Women's Size 7M Brown , Women's Skechers 14914/CHAR Go Walk 4-Fascinate Charcoal2017 fasion women men casual shoes flat for women menFlat Free People Evie Mary Jane Flat PinkSudini Lori Fashion Sneaker - Women's Size 7 Frappe , **Naturalizer Bayberry Flats - Women's Size 5 M - Porcelain , ADIDAS WOMENS SHOES SIZE 7.5 BLUE/ADIWEAR , Nike Benassi JDI Metallic QS Women's Slips Metallic Black AA4149-001 Size 11ADIDAS ORIGINALS ADILETTE WHITE CORE BLACK MENS SIZE AUTHENTIC SLIPPERS 280648 , Report Ammons Women’s Size 8 Black Leather Casual Fashion Sneaker Shoes F3-789 , NEW BALANCE Women's Abzorb Brown Leather Nubuck Hiking Shoes Size 9.5 B Gore Tex , Saucony Womens Omni Walker White Walking Shoes Size 8 (327678) , Asics Gel Preleus T480N Women's Hot Pink White Athletic Running Shoes - Size 9.5 , Skechers Synergy Elite Status Athletic Shoes - Women's Size 8.5, Black , Women's Manebi Espadrilles Blue Size 43 Be Novel In Design Flats , PONY SHOOTER '78 HIGH CHEVRON SNEAKERS WOMEN SHOES MIX 1781 SIZE 6.5 NEWAmazing St. Bernard Dog-Women's Running Shoes-Free ShippingNIKE EXPERIENCE RN 5 WOMEN'S RUNNING SHOESTretorn NYLITE6BOLD Sneakers - Women's Size 8.5 - WhiteASICS NIMBUS RUNNING SHOES WOMENS 10 TN485N FREE SHIP , Skechers Shape-Ups Toning Walking Shoes Women's Size US 10Vans Prairie Chukka MT Tan Black Women's 6 Skate Hiking Trail Shoes 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."