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.Steve Madden Womens P-Helena Woven Ballet Flat Shoes, Fuchsia, US 7Traditional Handmade Jutti Women Shoes Indian Leather Mojari Ballerinas US 9Okabashi brown closed toe Mule / Slides OKA B Womens US size mediumklogs Women's 7.5 M Multi Colored Leather Upper ClogsGeorge "Saturn 3" Black Flats Sz 8 , LIFE STRIDE brand Brown Bronze faux Patent Loafer Ballet Flats Shoes 8.5M , Anne Klein Drewe Link Loafers 892, White Multi, 7 US , LifeStride Womens indeed Closed Toe Slide Flats, Inky Navy, Size 8.5 fdCz , Tommy Hilfiger Womens Frank3 Leather Closed Toe Mules White Size 6.0 , Miramonte Black Velvet Flats Silver metalic Sequined beaded sparkle Shoes , Gray Leather or Faux CLARKS Cloudsteppers Sillian Bella Mary Jane Flats 7.5 MWomen's Sperry Top-Sider Intrepid Shoes Black & White Size 51/2 , Mix No 6 Womens Sarlinas Almond Toe Loafers Black Size 11.0 hFhX , Womens Clarks Unstructured Mules Size 10M Brown Leather Clogs Slides Slip-Ons , Lucky Brand Womens Size 7.5M Emmie Flats Leather Round Toe Ballet Black NWOB , ASICS Women's Gel-Kanbarra 5 White/Lightning/Apple Green Training Sneakers 8MB35 Hint Slip-On Sneakers 973, White, 6.5 US , Diesel Footwear Discovery Women’s 9 Leather Casual Fashion SneakersDenim & Supply Ralph Lauren Ramzey Low Top Sneaker Black Womens 7.5B US MSRP $49K-Swiss Tongue Twister Tennis Shoes Size 7.5 7 1/2 Med Women's WHITENEW Adidas Neo Women's/Ladies Cloudfoam Lite Racer Slip Running Shoes Black/Navy , CUSHION TRAINER NEW BALANCE LILAC MESH 755 N WOMENS TENNIS RUNNING SNEAKERS 7 , WOMENS SKECHERS GO WALK SHOES SN13756 Black Size 6.5Women's Adidas Pureboost Chinese New Year Quality First Athletic Shoes , ASICS Women's Gel-Fit Tempo 3 Cross TrainerAHNU~ MONTARA BREEZE Waterproof Hiking Trail Shoes Smoke Gray US 7 /38RARE? Nike SHOX Turbo Snakeskin University Ice Blue Carolina Sz 9.5 311079-141Oboz Luna Low Women's Mineral Blue Hiking Shoe 8.5MVans Women's Slip On Boat Shoes Size 10 Nautical Anchor Buttons Black Gray Tweed , More Mile Cheviot 4 All Terrain Trail Womens Running Shoes Navy ,
"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."