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.comfortveiw women black slip on shoes size 9WW , KORKS BY KORK-EASE Caramel Leather Studded Fashion Ballet Flats- 6.5 M 37 , CLARKS UNSTRUCTURED Brown Leather Loafer Moc WOMENS 6 M Shoes , SAS Tripad 12 S Comfort Simple Loafers Euc Black Leather , Franco Sarto Womens Porter Leather Closed Toe Mules, Black, Size 10.0 2I0T , Bed Stu Loafers Leather Sz 8 WomensLadies Clarks Comfortable Flats Everlay CodaBella Vita Channing Espadrille Flats, Champagne, 6 US , New Women's Skechers Bobs Bliss - Hot Cocoa Casual Flats (34145) (L16)Women's New Balance WW1870SB Walking Rolling Rocking Shoes Silver Blue 8.5 B , womans keen sneakers size 9.5 40Rockport Casual Black Leather Slip Ons 8.5M Women's cushioned sneaker look/fit , Stuart Weitzman Rialto Blue Goosebump Nappa Smoking Flat Size 7M D1799/Ryka Ultimate Running Shoes-Women's size 9.5 M GraySKECHERS Shape-Ups 11803 White/Silver/Blue Toning Walking Sneakers Womens 8 MWomens Nike Air Max Trainer Excel Shield 469766-001 Silver/Turquoise Size 8.5Skechers Women's On-The-Go Arena 13799 Athletic Sneaker Gray 168L02-1325 Rocket Dog Campo Beach Canvas Sneaker SIZE 8MSaucony Grid Propel Plus Running Walking Crossfit Casual Shoes WMNS. Size 9 ((A8Women's Roxy womens 10 Slip Ons Customers First FlatsVibram FiveFingers Alitza Loop Black Women's sizes 36-42 NEW!!! , VINTAGE RARE NIKE AIR JORDAN TRUNNER 302367-102 SIZE 7.5Lacoste Black High Top Womens BootAdidas Original Women's Tubular Shadow NEW AUTHENTIC Core Brown/Ash Green CQ2463NEW NIKE Women's Sz 5 Pale Gray White W Roshe Two BR Low Top Athletic SneakersNew Converse CT All Star Classic Shroud High Basketball Shoe /553460C MSRP $115New Women's Skechers 14300 Go Step Sport Walk Slip Ons - Black Size 6.5 (L13) , Women's RBK REEBOK Brown Athletic Shoes Size 8 (W-96)Brooks womens running pure grit athletic brown trail tie shoes SZ 8.5 BNike Tanjun Black Gold Running Shoes Youth Size 4 to 7 UNISEX New In Box ,
"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."