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.Sperry Top Sider Women's Boat Deck Shoes Size 6.5 M Weaved Leather Slip On , Woman’s T-Bar Leather Flat Shoe-Brand New-Size 7-Free Post-Bargain Price-CompareLiz Baker Brown Leather Slip On Style Loafers Women's Size 8.5MBaretraps Kessie Loafers, Women's Size 8 M, Taupe , EUC Clarks Collection Soft Cushion Mary Janes Sz 10 Suede Leather GraySuperdry JPN Snickers Shoes UNISEX Yellow Size EU-39 UK-6 , Munro American "Mallory" Women's sz 8.5 Black Suede Low Heel LoafersArcopedico Leina Mary Jane- Size 8AGL Ballet Flats SZ 38 Womens Shoes Leather Cap Toe Bronze BlackTrotters Womens sarina Closed Toe Ankle Strap Slingback Flats , Spelta Milano "Penelope" Flats with Ankle Straps SZ 7 & 9$89.99 Supra Women Cuttler (black / gold / white) SW35003 , Easy Street Womens Campus Leather Closed Toe Black Size 7.0 Cl20Clarks Raisie Theresa Slip On Loafer Flats 459, Black, 8.5 US / 39.5 EUNew Balance Womens Sz 9 Suede Cloth Sneakers Walking Shoes WW610GR Brown GrayNEW BALANCE 496 WW496WP WALKING SHOES WOMENS SIZE 9.5B , Steve Madden Womens Limit White Fashion Sneakers Shoes 10 Medium (B,M) BHFO 8200 , Women's Saucony Guide 8 Shoes Sneakers Size 9.5 Running Blue Gray Purple M9 , Women's Skechers Sneakers - Go Walk Joy-Rapture - Black/Hot Pink - New!Women's Ellie Women's Shane-511 Ample Supply And Prompt Delivery Athletic Shoes , Women's Red women flat shoe Inexpensive Flats , Women's Jelly Pop Size 3 Boots Ideal Gift For All Occasions Flats , Hogan 9.5 Black Tweed Panel Sneaker $450Womens nike free TR FIT 3 Running Yoga Crossfitt Size 12 Retail $95.002004 Nike Women's Running Shoe Sliver Pink Black size 9 (310144-001) max air , Women's New Balance WPACEBO Running Shoes - Blue/Red - NIB!CONVERSE ALL STAR WOMENS SIZE 7 GRAY WITH FLORAL TONGUE - 558553F - NIB , SKECHERS WOMENS GO RUN 600-REVEL ATHLETIC/RUNNING SHOES [15069/NAVY] , Diadora Women's Swan Running Shoe - Choose SZ/Color , On Cloud Womens Hiking Shoes Size 9.5 (3493) ,
"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."