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.Peacock Old Beijing Cloth Embroidered Shoes , NEW DOLCE VITA - WHITE LASER-CUT LEATHER HUARACHE LOAFERS/FLATS - LADIES 9.5LADIES SPOT ON GREEN SHOES "F80122" , New Ladies Women's Girls Pearls Sliders Slippers Glossy Sliders Flip Flops ShoesDolce Vita Women Lucy Velvet Loafers DV Flats Blue * 2 Different Sizes * 9.5 8.5SANUK TROPICAL SAILAWAY 2 NATURAL SIDEWALK SURFER BOAT SHOES, US 10/ ~NWTTahari Womens Frankie Closed Toe Loafers, Black, Size 6.5 oNAL , ECCO Women’s Size ~ US 9 Casual Comfort Shoes Leather Brown Sneakers EUC , Klogs Camila Women's Leather Clogs Display Model Shoes Black 7.5 MEasy Spirit Madella Pointed Toe Ballet Flats, Silver, 6 US DisplayNike Lunareclipse 2 + Running Shoes, Stealth/Pink/Volt, Womens 8WOMENS NIKE TRAINING FLEX EXPERIENCE RN3 - SIZE 7.5 lightweight , Asics Women's Hyper Rocket Girl SP 6 Size 7Trotters Women's Lamar Slip-On Loafer, Dark Brown, 6.5 2W USTom's Women Lenox Silver Metalic Leather.StyleSize: 8, 8.5, 9 NWOBOX , 12533 Skechers Women's Sport Sneaker, Grey/Hot PinkShellys London Elsie Grey Velvet Shoe Studded Slip-On White Platform Sneaker , Mens Soccer Slippers Official Product European Club Crest Football Game Slippers , *New* Reef Rover Low TX Shoes Women’s Size 8 Blue/green , Womens Skechers EZ Flex Memory Foam Slip On Shoes. Size 9. Nice Shoes! , ASICS GEL EXCITE 3 Womens Running Walking Shoes Sneakers T5B9N Silver Pink US 11Baskets Femme samples shoes ETNIES TOWNSEND BLUE WOMEN , NEW! Asics Women's gel Contend 3 Shoes Navy/Pink/Purple #T5F9N 102S zWomen's Qupid Women's Spyrock-05 Sneaker Inexpensive Athletic Shoes , NIKE WMNS PRESTO FLY (910569 300) SZ: WMNS 6.5 RETAIL: $100.00Women's Caterpillar Connexion Steel Toe Shoe, Green, 8 New , Women's Asics GT-2000 4 Running Shoes - Silver/Turquoise/Lime - NIB!ASICS Dynaflyte - Black - WomensNew Balance Women's Sneakers Black 600v2 6 D04Columbia Womens 1691191 Gray Fashion Sneaker Size 7.5 (32299) ,
"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."