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.Donald J Pliner Love S1 Black Casual Shoes Women's Size 8Ladies Shoes Spot On F9840 Black PU UK Sizes3-8 R10BOld Navy Orange Perforated Textile Espadrille Flats Slip Ons Women's Size 8Soda Faux Leather Pointy Toe Tie Up Wrap Around Ankle Ballet Flat Shoe Grey , NEW Banana Republic Angela Suede Leather Flat Shoes Beige Size 6 , jenn ardor Espadrille Sneakers for Women Hollow Canvas Casual Flats Classic S... , P.W. Minor Lady Melbourne Walking Shoes (19074) US Sz 8 A ~ MSRP $256 ~ WorkWalking Cradles Hamlet Slip On Loafers - Women's Size 9 M, Black , New Clarks Collection BLANCHE NORA Leather Women Shoes Sz 8SANITA PROFESSIONAL SIZE 40 MARY JANE BLACK LEATHER WOMEN'S 000LifeStride Womens Diverse Closed Toe Loafers, White Sand, Size 9.5 C0XsNike DART 7 Womens Size 7 Blue White Running Shoes 354138 ~ USEDAvia Women's Toning Sneaker-Arch Rocker~White/Pink Size 11 (Inv S3)Old Navy Shoes Womens Size 5 Black White Glitter High Tops Sparkles , MERRELL “CHAMELION” Women's Size 9 M Tan Suede/Fabric Casual Walking ShoesNew Balance 577 Womens 7.5 DSL-2 Walking Shoes Beige Sneakers Hook LoopWomen's adidas superstar originals women shoes Exquisite Workmanship Athletic Shoes , Women's LifeStride~8.5~Tan~Suede~Slip On~Loafers~Buckle~Leather Accent~Rubber Sole Colours Are Striking Flats , VANS Authentic (Nintendo) Duck Hunt Camo NES 8 Bit WOMEN'S Size 8 , AC91 WALKSAN by SUSIMODA shoes brown leather suede women sneakers , Vans OLD SKOOL Snake Black/Blanc Men's Shoes 8 - Women's 9.5 , Vans Sneakers Sk8-Hi Nightshade / White, Men 5, Women 7.5. NEW Purple-ish , NEW Womens MERRELL Kamori Eden J211104C Slip On Black Purple Sneakers Shoes , PUMA SUEDE HEART RESET ARUBA BLUE 36322901 WOMENS US SIZES , Asics GT 2170 Womens 10.5 Gray Purple Athletic Run Cross Training Sneakers ShoesAsics GT-2000 4 Women's Silver/Turquoise/Lime Punch Running Shoe 11MWomen's Skechers GO Step Lite Indulge Casual Sneaker 8.5 "Wide Fit" BlackNew CONVERSE ALL STAR Chuck Taylor Digital Floral Print OX Low Top Sneakers , Women's CONVERSE ALL STAR CHUCK TAYLOR OX 553325F White/Black Sneakers Shoes NewNike Free TR 6 SPCTRM Womens Blue Teal White Running Training 849804 300 size 7
"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."