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.Dolce Vita White Leather Monica Slip On Sandals Womens Size US 6M , Kelly & Katie Womens lovelian Closed Toe Loafers Navy Size 7.0 Tflf , BORN LEGATO DUSTY BLUE SHOES SZ 9 / 40.5 PLATFORM CLOGS MULES (B03) , EUC Minnetonka Moccasins Navy Blue Floral Accent Women’s 9 , Crocs women's clog shoes relaxed pink roomy fit size 6-7 , Women's Cole Haan Waterproof Slip-on Mules Black Zip Shoes-7.5 BSofft Macee Women Round Toe Suede Black Flats Size 6.5Tahari Vivian Ballet Flats Women Size 6 Floral Paisley Burgundy Wine LeatherBORN 7998 Navajo Aztec Multi-Color Wool Leather Mules Clogs sz 7 or 38 EXCELLENTBORN "Orin" Burgundy Flat NIB Womens 7M (38) , alegria womens 42 Sugar Skull Professional Clogs Multi Color ShoesTARYN ROSE CARESS Tangerine Metallic Gold Fleck Suede Driving Loafers Size 6 1/2 , Lauren Ralph Lauren womens CAITLYN platino metallic kidskin driving shoes 6 NEWSam & Libby Edelman Black Size 8.5 SOLID Velvet Bow Shoes , NWOB Keds Women’s Pink Low Top Shoes WF55683M Size 9.5 , Men's UNBRANDED Red+Black Plaid Fleece Slip On Scuffs Slippers House Shoes NEWArab - Muslim - Arabic Sandal, Slipper, Chappal - Islamic Naal for MensFILA 10 SHOUT CHEERLEADING LEATHER WHITE SHOES **WORN ONCE* IS WHY THE *DEFECT*Women's Nike Revolution 2 Gray Purple Blue and Pink Shoes 10 M , Womens ADIDAS ZX FLUX W Running Trainers S78090 , Skechers Performance Womens Go Golf? Eagle - Range, Black/White, Size 5.5PUMA Women's Vikky Platform 36524202 Velcro Sneaker Red Dahlia-Red Dahlia 8 M USASICS Women's Spivey LD Track ShoeKeds Women's Craze Ii Leather Fashion Sneaker, Black/Black, 9.5 M US , New Balance Women's Renew Thong Brown/White Synthetic PU Thong SandalsNike Lunar Control Oregon Ducks Womens Golf Sz 7 NEW 838116 108 RARENike Women's Air Max 90 Se, 881105 002 Gray/Black, Pre-Owned , Womens Nike Free RN Motion FK 2017 Size 8 (880846 004) No BoxRocket Dog Baker Electric Boogie Cotton Women's Shoes Size 9Cobb Hill Women's REVsea ~ Revlite slip on shoes (CBI08BK) ~ Black Leather ,
"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."