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.Crocs Alice Sz 8W Dark Grey Mary Jane Ballet Shoes , NEW COLE HAAN Womens' Nantucket Camp Moc Patent Leather Boat Shoes Navy Blue 10B , Sigerson Morrison - BLACK Italian leather Ankle Strap Flats - US size 8 - GUC , Women's Born W01269 Loafers Clogs Shoes Size 9M Beige Suede Shearling Lined D9Women's Skechers 14447/Choc Go Step- Modish ChocolateSperry Top-Sider Women 8 M Bahama Sequins Ivory Boat Deck Shoes 9447160 , Born Womens Black Leather Slip On Wedge Heel Mule Clog Shoe Sz 9 m EUC , Loeffler Randall Calf Hair Animal Print Pumps Heels Shoes Size 6.5 BDREW ACTIVITY WOMENS WHITE LEATHER OXFORD SHOES 9 NEW IN BOX , Aerosoles Women's Baby Girl Ballet Flat Black Snake Size 7.5 , Cole Haan Jenni II Beige Leather Buckle Ballet Flats Womens Size 6.5 MCLARKS Womens Kinzie Leather Closed Toe Loafers Pewter Leather Size 7.5 cQZMLL BEAN plum purple leather bumper toe hiking comfort cross trainer sneakers 7 , Touch Ups Women's Elite Slingback , FABULOUS NEW MARC JOSEPH MEDIUM BLUE LEATHER LOAFERS,GUMP CATALOG,SIZE 6 , Nike ACG Womens Size 6 Hiking ShoesNew Balance Women's W750v2 Running Shoe,750 Series NAVY Multi ,10 B US , Women's Brooks Pure Connect 2 running shoes size 9.5 , NEW!! Denali Incite Women's Hiking Boots Size 6 B52Women's Adidas Powerband Sport White/Gray/Powder Blue Golf Shoes Size 9 NEW! , Keds Red Slip On Open Back Sneakers Ladies Deck Shoes Size 7 Red PrelovedVANS Off the Wall Sneakers Neon Pink Canvas Shoes New Womens 7 Mens 5.5 Unisex , Nike Free TR Flynit 2 Trainers 904654-200, Chrome/Blush, Womens Size 8 / 39 , Adidas Superstar Shoes Women's - White / Black - Size 4Adidas Retro Multi Color Leather Wms Sz 9 High Top Sneaker Skate Basketball 6@ 3Vans Sk8 Hi Moc Suede Ivy Green Skate Shoes Size Men 8.5 Women 10 , VANS Sk8 Hi (Pig Suede/Fleece) Black/Blanc de Blanc Skate Shoes WOMEN'S 8 , Adidas Womens Adizero Tempo 8 Blue Running Shoes 10.5 Medium (B,M) BHFO 7669Women's Skechers Spirited Sneaker Black / White Size 6.5 #NG4EC-127 , WMNS NIKE LUNARGLIDE+2 COOL GREY WHITE ORANGE 407647-005 WOMENS US 9 red volt 8 ,
"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."