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 Black Silver Gold BL67 Rhinestone Mesh Mary Jane Ballet Flat SandalsParis Blues Kamila Gold Sparkle Slip On Shoes Size 6 Women's , Skechers 21279 Gold/Silver Leather/Textile Women's Mary Janes Walking Shoe 8.5 M , Women's Fabulous Flats Orange Suede Zipper Back Ankle Cuff Size 6PROPET Wash & Wear Slip-on Leather/Neoprene Orthotic Shoe Women's 8.5 X(2E) WideWomen's Naturalizer Comfort Walking Black Leather Slip-on Loafers/Shoes-6M , REMONTE Womens KATI 21 Black/Graphite Slip On Wedges US 8.5; (R9821-45) , Lila SureGrip Bella Women's Floral Multi Color Slip Resistant Clogs Size 9.5 , NEW Bernie Mev Women's Shoes 38 BrownGuess Adalina 2 Women Shoes Gold Bow Ballerina Flats Sz 9.5 MStubbs And Wootton Hunter Green Soccer Balls Size 9 , KEDS Striped 10 Tribal Canvas Sneakers Tennis Shoes Boho Bohemian African 90s , Nike Dual Fusion Run 2 Pink - Womens - Size 6 M , Womens Hollow Out Slip On Hidden Wedge loafers Casual Atheltic Sneakers shoes US , Women's Womens La Sportiv Bushido Special Offer Athletic Shoes , Women's LifeStride Women's Diana Flat Ideal Gift For All Occasions FlatsNike Women's Lunar Rift Racer Black/Pink Force/Ion Pink Running Shoe 9 M USNEW BALANCE WW812 Bone Leather Hook & Loop Walking Shoes SIZE 12 D newNike Flex Contact Women's Running Shoes Black White Anthracite 908995-001 Sz.6.5 , DS NIKE 2011 BLAZER MID BHM BLACK Unisex 6-10 SUPREME STUSSY DUNK SBSkechers Performance Women's Go Walk Joy-15609 SneakerNavy/Teal6.5 M US , 2007 Nike Air Max 90 Womens Athletic Running Shoes Size 8 White Volt Gray , NEW REEBOK CLASSICS MID JACQUARD BLACK SNEAKERS SIZE US 9Vans Womens Custom Authentic Lo Pro Sneaker Shoes Gray/Black/Blue 7.5 , Twisted Red Canvas Sneakers Size 10(Fits like an 8) Women's EUCNew Balance Womens - Blue Trail / Hiking Shoes Size 10 (366350)New Womens Nike High Blazer Red Sequin Sparkle Leather Shoes 403729-602 sz 7REEBOK NEW CLASSIC LEATHER AND SUEDE BLACK AND GREY WOMEN ROYAL CL JOG TRAINERSWomens Real Suede Leather Safety Trainers Casual Work Steel Toe Cap Shoe , Womens Brogue New Patent Leather Wedge Heels Creepers Punk Shoes Pumps Plus Size ,
"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."