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.Ladies Short Tassel Rabbit Snow Fur Lined Rain Winter Casual Warm Boot All Sizes , Clear/BLACK/SMOKE Fashion Beach Retro Flat Jellies Jello Sexy Sandals Size 8.5Rocket Dog Women's Chella Crush Fabric Ballet Flat, Grey, 9.5 M US , Women's Dr Martens Buckle Slip On 2A87 Black Size 5 EUC , Easy Spirit Womens Adriane2 Fabric Closed Toe Slide Flats , Loly in the Sky Bowtie Tan & Black Flats Women's size 7-7.5 , Vaneli Sport Women's Size 9.5 N Narrow Tan Suede Slip On Loafers Flats Shoes EUC , J CREW Nude/BlacK Leather Ballet Flat Sz 6 EXCELLENT COND , Skechers Flat Knit 59805H BLHP Memory Foam Sneakers [165E] , Nike Air Women's Black White Leather Golf Shoes - US 6.5 () , Womens Woven Shoes Slip On Elastic Flat Shoes Breathable Casual Sandals Fashion , Women's Clarks Wedge Artisans Slip Ons Size 6.5 (B,M) Casual Solid Black Leather , Easy Spirit Getcity Women Nude Ballet Flats Mtau/Mta L Size 9.0 wIZU , Justin Reece Womens Metalic All Leather Bow Ballerina Flat ShoeSHELLYS LONDON Edgar Pink Satin Platform Slip-On Platform Sneaker Oversized Bow , Women’s Sz. 9 Skechers Shape Ups Black 11809 , New Steve Madden Mens Pclinton Black Mule Slippers Size 13 (34510)Zoot Ultra Training Running Quick Tie Shoes Red Silver Women's Size 8 US/39 EUR , Nike Capri Leather Sneakers Shoes 7Y Eu 40Merrell Relay Stretch White Turquoise Athletic Shoes Womens Size 7Women's tory burch espadrille 8 Attractive Design FlatsUnisex Men's Women's Anti Skid Athletic Outdoor Sports Walking Sneakers Jogging , nike Air Huarache Run CROC Print OBSIDIAN NAVY US WOMENS SHOE SIZES 725076-401 , Azteca Horse Christmas Running Shoes For Women- Free Shipping , NEW Asics Onitsuka Tiger Mexico 66 shoe DL408 black unisex mens 4 / womens 5.5Nike Women's FREE 5.0 TR FIT 5 PRINT Shoes Black/Pink 704695-011 a1Nike Flyknit One Shoes Women's Size 9WOMEN'S PUMA FIERCE BRIGHT 189738 03 PUMA WHITE BRAND NEW DEADSTOCKRetro Womens Rivet Flat Heel Ankle Boots Fashion Pull On Cow Leather Boots Sz , New Balance WCOASSL : Women's Vazee Coast Running Shoe, Silver/White ,
"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."