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.Forever 21 faux suede penny loafers sz 7.5 , Born Handcrafted Womens 11 / 43 Red Leather Mary Jane Buckle Flat Loafer ShoesHavaianas Women's Origine Sneaker III Espadrille, White, Size 10.0Kaanas St. Lucia Peonies Magenta Espadrille Slip on Shoe Flats 10M 10 40 $99 New , Womens Bow Tie Round Flat Shoe Moccasin Driving Shoes Soft Boat Ballet All SizeWomen's Xhilaration Ballerina Shoes Black Sz 6.5"Liz Claiborne cream and black cap toe flats 9.5 , New MIA GIRL BRANDY OXBLOOD WOVEN FLATS SHOES 6.5 M , **Cliffs by White Mountain Bridgette Shoes - Women's Size 6M, BlackFranco Sarto Leather Slip-ons w/Espadrille Trim-Ironic (1646) Black Sz 9.5M CRBurgandy Patten Leather Mules Slides Scuffs Casual Dress Shoes Ladies Womens 7Ladies Clarks Casual Slip On Flat Shoes Label - Clovelly SunEasy Spirit Women's Kickit Wedge Sandal Gold Leather Size 10 MKimchi Blue Coral Pink Orange Pumps 10 41RARE PAOLA CAVALLI PURPLE LEATHER mule clog slides shoes colorful studded band 6** Aerosoles Test Drive Faux Leather Loafers, Women's - Size 8 M, NavyNew Artificial Intelligence Denmark Colgs Health Well women's sz US 9.5 , clarks espadrilles Womens 8 Azella Theoni Snakeskin Comfort Cushion Sole ShoesMODA SPANA WOMEN'S TAMARA JEWELED BALLET FLATS BLACK SUEDE US SIZE 7 MEDIUM (B)M , ADRIENNE VITTADINI Footwear Women's Corin Ballet Flat Black Size 8.0Funky Womens Floral Canvas Shoes Hi-top Sneaker Boots Ankle Shoes Casual Sports , Skechers Womens Synergy - Case Closed Casual ShoeWomen US- Pick SZ/Color. , Women's NIKKEN Exercise Cardiovascular Workout Walking Weighted Shoes 8 1/2 $200New! Women's Puma 35421705-05 Athletic Shoes - SIZE 7 Black/Pink E24Women's Bass Milly Size 8 Online Outlet Store FlatsAsics Tiger Women Gel-Lyte V black black H661L-9090Nike W In-Season TR 7 Cross Training Womens Shoes Black Silver 909009-001 SZASICS Womens Gel-Fujitrabuco 6 Running-ShoesM- Pick SZ/Color. , ASICS GT-2000 5 Sneaker - Women's Size 11 Gray/White/Pinkcolumbia Womens Powerdrain Cool Trail Shoes US Size 10 ,
"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."