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.Lavender A New Day Faux Velvet Slides Size 9 New NWTClarks Everyday Active Loafers Women's 7 N Black Suede Patent Leather Shoes 106EUC Banana Republic Flats Ballerinas Mocasins Tan Leather Beige Size 7Lot Of 2 Steve Madden Womens 6 Slip On Mules SPIDERR Black Red White StripesJ.RENEE Cotton Flats Pre Owned Womens Shoes Size 6.5M Gray , Enzo Angiolini Women's Gold Leather Slip On Moccasin Loafers Shoes Size 7.5 M , Womens Size 8 Born Brown Leather Wedge Loafers , Lucky Brand womens clogs size 8.5 M slip on wooden peace sign tooled leather , Women's Lands' End Brown Suede Loafers US 7B SZ Very Clean! Excellent condition! , Bamboo Womens Sami Metal Bow-detail Ballet FlatsWomens Fleece Heel Suede Lined Fur Faux Flat Faux Knee Boots Trim Sizes , Donald J Pliner 11 Black Suede Oxford Platform Shoes Women's , New VINCE CAMUTO Soft Blue Leather Tassel Toe Ballet Flats BETSEY 6M/36 , New Women's Dansko Loretta Black Platform Oxford US 6ZIERA sz 43 FF womens black OVATION Leather shoes - Current collection [#F77] , EUC New Balance 80 Womens All Terrain Shoes Brown/Turquoise/Lime Green Sz 8B(US) , Womens Slip On Loafers Rabbit Fur Casual Shoes Flats Heel Slipper Fall LeatherWomens Wedge Heel Peep Toe Sneakers High Top Buckle Strappy Platform ZsellBrooks PureConnect 4 Womens Size 8.5 Running Shoes Black Pink M3Women's NEW REEBOK WOMENS PRINCESS WIDE Superior Quality Athletic Shoes , Men's Shoes Slippers Glerups Boot Slipper Green 37.0 To Adopt Slippers , Women's VICTORIA Toile 106613 Bleu Foncé Quality Product Athletic ShoesCONVERSE CHUCK TAYLOR ALL STAR CT AS HI PERFORATED 551627F REBEL TEAL/WHITE/BLK , ADIDAS DECADE MID WOMEN'S SHOES BLUE/RED/WHITE Q20675 SIZE 10Women's Nike Blazer Mid Orion Blue/Grape Sneaker: Size 11 M , Nike Max Air 180 Rare Vintage Airmax Revolution Lime History of Air 2005 6.5Women's Asics Gel-Cumulus 16 Black Onyx Running Shoes T489N sz 7.5?Authentic Adidas Ultra Boots Uncaged 7 1/2 , Saucony Guide 8 Running Womens Size 8 , SPERRY TOP SIDER perforated cute ballet flats boat shoes with bow accent 8 m
"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."