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.Born Shoes 6-1/2 (37) Women's Brown Leather Clogs , Christian Siriano Black Faux Suede Jeweled Ballet Flat Shoes Womens 8 CasualAerosoles Backbend Slip-On Loafers, Black Leather, 6.5 USCLARKS Black Leather Slide On Wedge Button Clogs Mules Womens Shoes Size 7.5 M , Aldo Ballet Slip on Shoes Black w/ Chain Accents size 6.5 /37Earth Black Leather PATTIE Peep Toe Sandal--size 10MSAS Loafers Womens Shoes 8.5N Metallic Gold Silver USA Slip Ons Casual 7224Blue Suede Shoes Black And White Flats Size 9 WomensRag & Bone Black Leather Flat Espadrilles Shoes Size 7 , **Sam Edelman Brandi Flats - Women's Size 8.5 M - FuchsiaNew Women's Bowknot Loafers Moccasins Leather Casual Flats Slip On Fashion Shoes , BORN Womens Shoes Black Leather Mary Jane Loafers Size 8.5 , Klogs Kravings NAOMI Women's Clogs IRON Leather Display Model Shoes 8 M , Sanita Women's 8.5-9 US 39 EU Danish Design Liquicell Leather Clogs Tan PERFECT , Womens Skechers memory foam thong Sandals - size 8 - white , NIKE! Women Burgundy with Gold Accent! 7 (used)Audrey Brooke Womens Mojito Leather Closed Toe Ballet Flats Black Size 6.0 zKf , Guide Gear Men's Suede Slippers, Suede, Rubber Sole, Wool Blend Lined, US 13 MedWomen's K SWISS White/Pinkish Purple Leather Sneakers SZ US 6.5 , Brooks Ghost 7 Womens Size 9 Running Shoes Pink/Orange/Yellow , Converse All Star Ladies Black Canvas High Top Folded Shoes Size 5.5 (usa) , MG35 Brooke Slip on Low Top Sneakers 267, White, 8.5 US , Womens Saucony Cohesion 9 Shoes Sneakers Size 6.5New Balance WZ501POG Shoes Womens Size 8.5 NWOTU.S. Polo Assn. Women's Cara-E Oxford - Choose SZ/Color , Women's totes Women's Rhonda Black Waterproof Colours Are Striking Athletic Shoes , Adidas Women's Superstar Originals Casual Cheetah Shoe Size 6.5 NIBChaco KENDRY-W WomenS Kendry Trail Hiking Shoe SIZE 5 NEWwomens Nike air max thea size 8.5 pink gray eucNike Womens US 8.5 Tan Retro Decoupage Dunk High Tops Sneakers 432172-100 ,
"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."