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 Loafers Brown Leather Braid Detail Block Heel Size 9 MMarc Fisher Slip-on Flats w/Jewel Accents - Cadassi Silver (1677) Size 6.5M , Ladies Savannah Flat Shoes Label F80053 , Lucky Brand Womens Flats Size 7.5B US Brielly Leather Shoes 37.5Ariat Black Brown Leather Mules Slides Slip On Shoes 2 Tone Womens 8 B SN 94302 , Massimo Matteo Nappa Penny Loafer - Women's Size 7 B, Black , Sperry Top-Sider Womens Bluefish 2 Eye Linen Oat 9276619 Boat Shoes sz 6.5M , Skechers Pureflex Supastar Slip On - Women's Size 9.5 Black , Sperry Top-Sider Tan Brown Oxfords Women's Leather Shoes Size 7.5 MSporto Womens Shoes Size 8.5 NWT Mule Black Jessica Casual Slip OnAlegria Womens Flair, Black Nappa, Mary Jane, Wedge Pump, Size 10.5, FLA-601 , Reebok Running Shoes Sneakers Women Size 7 Great ConditionNew Balance Womens Running Reflection/RoseGold Running Shoes Size 9.5 (309795)Women's Natural Sport Cradle WHITE ATHLETIC WALKING SHOES Size 6.5 WLaPlume, Paolo, Gold Metallic, Size 37 Flat, Anti-Shock Sole , Converse Womens Grape/White Fashion Sneaker Size 10 (28578) , New Skechers Women Sz. 8.5 Alpha-Lite-Fair Share Walking Casual Sneakers BlueSkechers Women's Summits Sneaker, White, Size 6.5 0kep , Women's BALLERINES SOIR DE LUNE 39 Quality Products FlatsVibram FiveFingers Seeya LS Running Shoes *NEW* Black/Grey/Rose Size 37 , Rocket Dog Women's Mack Ankle Bootie Grey Polyurethane Zipper , PROPET W3840 WOMEN'S DIABETIC WALKING SHOES 9 M (B) BONE/WHITE *NEW*Adidas Originals Womens Superstar Coral Peach White Sneakers Shoes Size 7.5 NWT , New Balance Womens Classic Walking Shoe Sz 6 B Casual Comfort sneakersWomen's Nike Zoom Condition TR Training Shoes NEW Grey / Mint / White , MSRP $90K-Swiss Women's Clean Court CMF SneakerVN08EMNQ8 Vans Women Authentic - Velvet navySkechers Size 8M Flex Appeal Air Cooled Memory Foam Sneaker Blue Adjustable BungAravon Women's Wembly Mary Jane Fashion Sneaker, Blue Size 7 1/2 Wide , Elie Tahari Womens viceroy Low Top Slip On Fashion shark/denim/slvr Size 5.0
"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."