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.Born Mary Jane Flats Womens 7.5 M Brown Leather Slip On , TRANSAT BOUTIQUE BALLERINES "ILOUNA" NOIR 38 - PRIX PROMO!Marsh Landing Size 7 Brown Tassel Loafers Women'sClark's Women's Slip On Clogs Mules Shoes Leather Brown Size 11MWomens Aetrex Black Mary Jane Size10.5" X-Wide Stretch Fabric Comfortable CustomBernie Mev Silver Comfi Women's Shoes size 38 SilverSAS Loafers Shoes Slip On Brown Tripad Comfort METRO Horsebit Leather ComfortIndigo Rd. Griff2 Pointed Toe Ballet Flats 559, Gold, 8.5 US , New SAS Me Too Women's TAUPE Leather Tripad Comfort Shoes - US 9.5 N , NWB, ANNA by Swedish Clogs, Navy Blue Nubuck Leather Stapled Clogs, US 7M , Women's Salvatore Ferragamo Deep Bronze Leather Dress Loafers US 9.5 4ANew Women's Skechers 13522 Go Walk Everyday Ballet Flats - Navy Size 6 (Z2)Shoes athletic womens size 12M new man made materials Cross TrekkersNew Balance 615 white silver pink walking womens ladies tennis ww615km Size 9 , NIKE FREE RUN 2 HOT PINK BLACK WOMENS 7 EUC SUPERCLEAN see pics-detailsAldo Womens Galinsky Leather Pointed Toe Loafers White Size 8.0 lf0k , Nike Womens Black Primo Court Canvas Casual Shoe?631635 MISMATCH US 10.5/11Skechers D’Lites Womens 11936W Athletic Shoes Size 8, Grey/White 964New Balance KJ880BPY Athletic Running Training Shoes Sneakers Gray Pink Womens 7 , Women Hidden Wedge Heels Sneaker 2018 Mesh Platform Leisure Shoes Creeper NewDOMO 3D Plush Slippers with Embroidered Eyes & Teeth Men's ADULT SIZES M, L & XLNEW ROCKET DOG DEAN METALLIC SNEAKER SHOES WOMENS 7.5 HIGH TOPS CASUAL SNEAKER , NEW BALANCE WOmens Size 6 Black COMFORT RIDE 520v2 Walking Running SNEAKERPropet Tour Walker Strap Diabetic Walking Shoes, Women's Size 8D, White , Women's clarks shoes womens size 10 Various Styles Flats , VANS Classic Slip On (Suede Embossed Weave) Port Royale True White Womens 5.5 , Saucony COHESION 9 Women’s Running shoes, BLUE Size US 7, UK5, Eur 38 , Skechers Performance Womens Go Step Pose Walking ShoeBlack/White8.5 M USNIB Asics MetroLyte Q651N-0601 Shoe Coral Neon Orange White Womens Sz 6 - 11 , 14965 Gray You By Skechers shoes Women Slip On Comfort Casual Walk Flex Knit New ,
"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."