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.Tan nn Strappy Point Toe Fashion Womens Ballet Flats Dress Shoes Size 6OLD NAVY SLIP ON STRAW ESPADRILLES FOR WOMEN BLACK AND BROWN SIZES 6, 8,9 AND 10 , NATURALIZER N5 MEMORY FOAM COMFORT - 2-TONE BROWN SPORTY FLATS - LADIES 9M , Liz Claiborne New York MIGGY Black Loafers, Size 7 , New Women Light Grey Soft Line Leather Flat Shoes USA 9 , Mossimo Women's Brown Textile Slip On Ballet Flat Shoes US Size 6.5ICON Women's Black Leather ARTWORK Loafers Flats Shoes Size 7M USAMeeshine Women's Wedding Flats Comfort Ballet Flats Shoes New Gold 7 USThe SAK Sakroots Womens Emi Espadrille Sandal Neon Wild Life 7 M US Style 107744 , Baretraps Polina Black Womens Shoes Size 9.5 M Flats MSRP $69 , Mojari US 6/7 Indian Women Shoes Handmade Slippers Flip-Flops Leather Clogs , NEW Free People Evie Mary Jane Flats Green Velvet Sizes 38 + 39 , Munro American Penny Heels Pumps Shoes Sz 8 SS Beige White Womens 1AB , Ballerines Souples à Brides JOSE SAENZ Cuir Marron T 38 TBE , Hotter Womens Angel Shoes Black Suede Patent Leather Slip On Cap Toe Wedge 8.5 , BORN BOC Womens Peggy Black Leather Slip On Clogs Shoes Size 7.5 , Marc Fisher New Black Gold Metal Accent Slip On Loafers Comfy Shoes Flats sz 7 M , SAS Women Kiltie Loafer 9N Maroon Red Leather Fringe Tripad Comfort Handsewn USA , Mizuno Wave Legend 3 Pink and teal / aqua running shoes 9.5 US , NEW WMNS NIKE PRESTIGE 3 SKINNY HIGH SZ 9.5 PINK/GREY/WHT CASUAL 551649 661HOT NEW STYLISH LIFESTYLE MEN k-06 BLUE WINTER SLIPPER MADE OF COTTONUnder Armour Womens UA Speedtire Ascent Mid Running Shoe, Bayou Blue, 8.5 M US , Merrell Shoes Sprint Spin Cutter Women's Gold Pearl Size 5.5Women's converse all star sneakers Womens Aesthetic Appearance Athletic Shoes , Merrell Women's 1SIX8 MJ AC Athletic Mary Jane Sneaker J45706 Wmn Sz9M US Eur 40 , JUICY COUTURE Darren Black or Maroon Velvet Flat Sneakers Shoes NEW Womens Sz 6PUMA Womens Roma Basic Classic Sneaker- Pick SZ/Color. , Merrell Siren Edge Women's Monument WP Hiking Shoes 6MReebok Classic Princess Black Gum For Women's 5 To 10.5 New In Box 100% Original , Sam Edelman Womens Elton Pink Mauve Dupioni Fashion Sneaker Size 7 (23382)
"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."