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.Clarks Mules Slides Black Leather Womens Slip On Shoes Size 8.5M , Women's Shoes Size 7 M KLOGS Brown Leather Clogs Slip Resistant Soles , Steve Madden Women's Syruss Flat Sandal Pink Size 9.5M , Madness Tan Loafer Flats Sizes 6, 6.5, 7 NWBSam Edelman Sebastian zebra boat shoes 9.5MSofft Clogs Western Cowgirl Brown Leather Studded Tooled Floral Design 9 MBandolino Fadri Ballet Flat - Ballet - 8 M , The Walking Co (Portugal) blue tan size 42 beach style weave w leather low slide , STUART WEITZMAN 9.5 Low Heels Wedges Tortoise Patent Leather Pumps , Dansko Kate Stone Nubuck Leather Mary Janes Women's 36 US5.5 Shoe Distressed EUCWORN ONCE 8 M SAS SIMPLIFY BROWN PATENT CROC SHOE WOMENS LOAFERSpring Step Manila Black Women's slip on Shoes 7W343851 006 NIKE AIR MAX TORCH 4 Women's Shoes Black/Pink Pick Size 7 , Steve Madden Jecntrcq Girl's Black Fashion Sneakers 1M , Steve Madden Karry Black Suede Perforated Jeweled Loafer NEW , NEW! Men's Brown Soft Sole Booty Style Sheepskin Slippers Real Leather all sizesNike Airmax Women's Go Strong Running Shoes Black/Turq/Pink Size 9.5(US) , Propet Women's Washable Walker Walking Shoe, Sr White, 11 M US , New Balance 928v2 US 7 Black Walking Shoe Women'sUnder Armour W Threadborne Shift Cardinal Red/Dark Maroon 3019918-600 SZ 9.5 , SUPERGA 11117 PINK ROSE SNEAKERS SZ 37.5NIKE WOMENS AIR FORCE 1 PREMIUM URBAN HAZE GREEN BLUE WMNS SZ 6-12 315186-341 , Nike AIR MAX THEA PREMIUM LEATHER Women's Sneakers size 7.5 - Metallic PlatinumNew in Box ~ New Balance Women's Size 10 WW928 Walking Shoes - White , New Balance Vazee Rush Running Shoes Black-Womens Size 5D-Pre OwnedCLARKS 202286 CINDY WOMEN'S WHITE CASUAL SNEAKERS NEW IN BOX 9 MED A , Womens Size 8 Converse Chuck Taylor Sneakers Gemma Fiberglass 555841CWomen's Skechers Shape Ups Walking Shoes Size 7.5 Toners Toning Firm Black White , Womens NEW BALANCE W575BK1 Black & Purple Walking Running Shoes SIZE 7.5New Balance 999 Womens Leather Athletic Country Walking Shoes Size 9.5 Brown ,
"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."