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.Ladies Flat Satin Ballerina with Bow Trim and Floral Print F80292 , Women's Cole Haan Tassel Slip On Mocs Size 8 (B,M) Casual Solid Black LeatherNAOT Women's Clogs Green Leather Black Wedge Slip-on Mules Split Toe Shoes 41 10Easy Street Women's Giddy Ii Flat, Tan, 7.5 M US , LOUIE By RICHTER White & Brown Leather "Derby" Oxford Shoes, 41/US 9.5 Italy-B1Kravings by Klogs Womens ASTORIA Shoes Display Model SUNTAN 8 M , New Sperry Top-sider Firefish Snake Women's Deck Boat Shoes Linen 9 , Anne Klein AK Sport Women's Oksie Fabric Ballet Flat , Kenneth Cole Wilhemina Black Womens Shoes Size 5.5 M Flats MSRP $120 , New Beira Rio Tecido Womens Cushioned Active Casual Shoes Made In Brazil , Vans x Hello Kitty Pink HK Print Slip-on Sneakers Size W9.5 , Nike Flex Trainer 5 Size 7 Running Training Shoes Womens Grey Volt 724858 004 , Womens NIKE Lunarlon Flyknit 9.5 EUCTrotters Women's Arnello Ballet Flat, Dark Brown/Black, 11 N US , New Square Toe Womens Metal Decor Pumps Leather Loafers Oxfords Shoes Comfort SZMarc Fisher Womens Comrad Leather Closed Toe Loafers, Brown, Size 7.0 , Womens Saucony Liberate Running, Cross Training shoes size 7NIKE Shell Top Mule Sneaker Women's 7.5 Low Top Slip-On 315848-381 Brown/Orange , WOMENS NIKE LUNARGLIDE 7 GREY & PINK RUNNING SHOES SIZE US 12Womens Sneakers Size 9 Triple S FashionConverse Trainers Breakpoint Ox 155795c Cream , WMNS NIKE AF1 ULTRA FORCE MID PRT (U.S) SZ: WMNS 5 (807384 600)Skechers 23235 Womens Breathe-Easy-Flawless Look Sneaker- Choose SZ/Color. , Nike Air Pegasus 30 Womens Running Shoes 599392-404 Size 8.5 , Skechers You Define - Perfection Gray Womens Sporty Walking Shoes Size 6M , Puma Women's Volita Training Shoe, Gray/White/Green/Lime, Size 9.5 M USNike Superflyte Women Shoes Size 8 New! , New Balance 240 Womens 10 M Blue Silver Hibiscus Track Field Floral Running ShoeNew Balance WZANTOG3 Athletic Shoes - Women's Size 7.5 B, Slate , Womens Size 6.5,7,8.5,10 NIKE CITY TRAINER 909013 COOL GRAY WHITE VIOLET
"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."