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.New Women CHeRISH Leciliaa-1 Metallic PU Pointy Toe d'Orsay Ankle Strap Flat , Clarks Artisan Mules Clogs Maroon Burgundy Leather With Buckle Women Size 7 M , CLARKS Women's Privo Brown Suede Mary Jane Wedge Strap Shoes 76012 Size 8.5M , Best Price Plus Size 34-44 2017 Women Flat Shoes Woman Summer Flats Hollow Out CSanita O2 Lite Tranquility Women's Walking Shoes - (US 9-9.5) , Lands End, Brown Slip on Loafers, Women's Size 8M, 84623 Y112 , New Talbots Quin Size 5.5 Red Crocodile Embossed Leather Loafers Boat ShoesSanuk Women's Mya Flat Orange/Multi Size 7.0DOUBLE H BOOTS Women's Brown Leather Slide Mule Clog Western Shoes Size 6 / 36.5 , B.O.C. Katina Mule Clog Black Leather Shoe Comfort $80 Quality Styllish Nice 6LADIES CLARKS BLACK SLIP ON LEATHER SHOES UK SIZEs 3-9 GEORGIA E FITTINGKlogs Kravings Blaine Clogs Womens Display Model Shoes Iron 11 MMINNETONKA MOCCASIN Thunderbird Boat Moc Shoes Sz 6 - PINK SUEDE LEATHER BeadedSkechers Air-Cooled Memory Foam Sneakers Women's Size 8Women's Converse Chuck Taylor Double Tongue High Top Purple/Plaid Sz 6Salvatore Ferragamo Black Suede Kiltie Loafers Women's Size 5.5 B Shoes , Keen Womens Size 9.5 eu 40 Brown Elastic Strap Leather Mary Jane Shoes MoraLands End Men's Driving Moccasin 470873 Brown Leather Shoes Sz 9.5 EUCAsics GT 2000 Running Shoes Women Size 6Women's Maiden Lane Slip-On Leather Sneaker Easy To Use Athletic ShoesWomen's Keds Slip-on Sneakers-Size 7M-Anchor Palms Customers First Athletic ShoesNew Under Armour Performance Spikeless Golf Shoes White 1297176-141 Wms Sz 9Vince Camuto Dalmi Espadrille Slip On Sneakers 113, Black/Cloud Cream, 6 US / 36New Women Vans Authentic Black Skateboarding Shoes Classic Canvas size US 6 , Women's Nike Air Max+ 2010 Silver/Lime/Blue Running Sneaker (8)NEW Madden Girl Adorree High Top Black Sneakers Shoes sz 8 , REALTREE GIRL MAMBA XTRA CAMO & Orange Ladies SHOES, HIKING, CAMPING 12 wBurnetie Women's Fresh Hi High Top 296272 , Free People Velvet Black And Metallic Purple Flat Sneakers Shoes Size 9Womens Nike Sky high wedges navy 8.5 ,
"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."