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.Rockedog C2561110 Women's Grey Round Toe Ballet Flats US Size 7.5 M , Under Armour Flip Flops Sandals 4D Foam Black 11 43Plimingo Women's Black Glitter Leather Ballet Flat Shoes Size US 6 MM , Simple Suede shoes, women's size 8.5 US Sand color , COLE HAAN Amalia Skimmer Half D’orsay Flats Blue Women Size 8B Pointed Shoes , J CREW $125 Women's Gold Marsala Ballet Flats Shoes 6.5 NWOB Cutout Laser Cut , Women's Dansko Mary Janes Size 6.5 (B,M) Casual Solid Brown Leather , JOAN AND DAVID AMAZING BROWN & TAN LEOPARD PRINT PONY HAIR TOE BALLET FLATS 7.5BCBGeneration Women’s Beige Flat Size 10B Shoes925 Women's Shoes Size 9.5 M BlackDr Martens Womens Brown Leather Super Chunky Creeper Oxfords England US Size 7Womens DANSKO cognac brown leather Mary Jane flats sz. 39 $120Jeffrey Campbell Nereo-St Black Silver Tufts Fur Mule Slip On Slides (8.5)LUICHINY $84 BLACK SLIP ON FAUX LEATHER ATHLETIC Casual SHOES SNEAKERS SZ 6.5Pastry Glam Pie Alpine Casual Shoes PA123125 Grey Aqua Brand New Womens 7.5Keen Dry S3 Women Sz 8 Gray Brown Carbon Rubber Sole Hiking Athletic Boot ShoeFila Women's Pilota Memory Foam Breathable Slip On ShoesSkechers Microburst All Mine Womens Memory Foam Shoes , BIRKENSTOCK PROFI BIRKI 43/M10L12 R New! 074081Pr!vo by Clarks Beige Walking Shoes Women's Sz 6.5 Medium M Suede Low Pull OnMarc Fisher Xena Platform Shoes - Women's Size 5.5 M, White/SilverTommy Hilfiger Vilma Low Top Sneakers Size 6.5 Red White BlueAthletic Works Linda Slip On Shoes Sneakers Brown Size USA 10 Eur 42 1/2 , Women's adidas Womens Adicross Golf Trainers Unusual Athletic ShoesAsics T676N GEL NOOSA TRI II Womens Shoes Multi-color Sneaker Size 6 1/2 , New Adidas Adezero Rubber Shoes Women Neon Lime Green Very Light Sz 7.5 Unisex , Womens NIKE ROSHE ONE FLYKNIT Gym Red Trainers 704927 601WOMEN'S PUMA FIERCE BRIGHT 189738 03 PUMA WHITE BRAND NEW DEADSTOCKVIONIC 555 WILLA SZ 6 Women's Casual Shoes Bronze Metallic, , The Fix Women's Jasper Slip-On Tassel Fringe Fashion Sneaker ,
"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."