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.NEW Clear Fashion Beach Retro Flat Jellies Jello Sexy Sandals Size 8Womens Sperry Top-Sider Tan Silver & Pink Leather Boat / Deck Shoe Loafer 6 MINC International Concepts Caleyy7 Espadrille Flats 710, Silver, 8 US , Ryka Size 9 Blue Slip On Shoe WomensTraditional Indian Handmade Women Shoes Flip-Flops Mojari Juti Ballet Flats US 4 , COLE HAAN Air Women's Brown Leather Slip On Flats Shoes Size 7.5 B**Easy Spirit EZ Cool Slip On Clogs - Women's Size 7 W - Black , Dansko Brown Leather Tooled Slip On Clog Sandals Women’s Size 39 US 8 , Nine West Womens Zavanna Leather Almond Toe Ankle Wrap Ballet, Lt pink, Size 8.5SAS White Free Time Tri Pad Comfort Selfset Walking Shoes USA Womens 10.5 S SlimNINA Classic Ballet Flats Leather Velvet Cute Bow Comfort Shoe Sz 7.5 M ItalySAS Tripad Women's Size 9.5 M Brown Leather Mary Janes Roamer Comfort Shoes , Minnetonka Womens twill junior trapper Closed Toe, Cinnamon, Size 8.0 UDguCole Haan Womens Angelikasam Closed Toe Boat Shoes, Silver, Size 6.0 , Franco Sarto Sz 9.5 M Silver Metallic Shiny Nova Oxford Loafer Flatform SneakersB35 Hint Slip-On Sneakers 348, White, 5 USWomen Sports Running Sneakers Leather Increase Casual Outdoor Shoes , Loretta Slip on Sneakers Navy & White Stripes by Mossimo Supply Co. Womens NWTDansko Hailey Brown Leather Slip On Clogs Women's Sandals Size US 5.5-6 /CLARKS Womens 9M Black Leather Suede Sneakers Walking Shoes Size Athletic ShoesNew Nike Zoom Rival M Multi-Use Running Track Women's Size 8 806559-403 W/spikesSperry Top-Sider Firefish Women's Rainbow Black Boat Shoe 5MWomen Vans Old Skool True white Skateboarding Shoes Classic Canvas size US*6.5New FILA Womens CENTER COURT B BLACK FS1SIA3091X UNISEX SIZE TAKSEWomen's Nike Flyknit Zoom Agility Training Shoes NEW Blue/Black/White, MSRP $150Skechers Bobs Bob's Squad-Sky Write Women's SneakerSKECHERS SHAPE UPS Size 8 Gray LEATHER SNEAKERS WALKING Tone EXCELLENT 030041 , Fila Memory XRidge Sneakers - Women's Size 8.5, Grey/Pink/Blue , Clarks Wavewalk 8.5 Black Walking Shoes Women'sMerrell Womens Purple Horizon Blue Athletic Shoes US 11 Sneakers Trail Shoe
"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."