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.Women Flat Shoes Fahion Spike Studded Casual Slip On Style Two Tone Design , Hush Puppies Red Boston Leather Loafers Shoes 10 Women's New NWOBSODA ~ WOMENS FLATS ~ NAVY LINEN ~ VERY COMFORTABLE ~ SHOESIndian Handmade Rajasthani Light Golden With Black Thread Work Mirror juti Women , Minnetonka Red Fringe Tie Thunderbird Beaded Moccasins Women’s Sze 7 Barely WornBorn Boylenn Brogue Tassle Kilty Loafer Women size 7.5 M Dark Gray Leather , Women's Juicy Couture Size 8M Silver Metallic Black Mid Fashion Sneakers Shoe I9 , Earth Tayberry Women's Slip On, Blue, Size 6.5 RPBOLand's End Shoes Mules Clogs Women's Sz 8B Red Leather Suede Upper Nurse WorkNew Talbots Ivory Leather Driving Mocs Loafers sz 6B , Brinley Co Women's Edie Ballet Flat, Black, Size 8.0 2DpU , Eileen Fisher Sz 8 Ballet Flats Glee Dusted Brown Suede Leather Bow Shoes , FIORELLA CLUB LEATHER OXFORDS WOMEN SIZE US 8 - 8.5 HOT MADE IN ITALY , DANSKO WOMENS SHERISE MULES FULL GRAIN BLACK LEATHER OPEN BACK CLOG SIZE 39 VG! , Klogs Nicole Womens Clog Shoes Display Model Leather Blue Spruce 8M , Women's Birkenstock Birki's Olive Pebbled Clogs Mules. 6 N Equivalent to a US M , Dexter Women's Yarmouth Golf Spike Shoe White/Biege Size 7.5M NWOB! , Women's Pointed Toe Slip On Loafers Multi Color Embroidery Flowers Pumps Flat SzGrasshoppers Ashland Casual Shoes - Women's Size 9.5 M, WhiteRyka Womens Black/Grey Sandals Size 9.5 (C,D,W) (30684) , Bella Vita Women's Ezra Fashion Sneaker, Black/Crackle, 7.5 N US , Empty New Balance Sneaker Box Gray No Sneakers Included Just The BoxNike Women's Flex Fury Running Shoes 6RNew balance running shoes women's 9 gray pink white WR8709PW SNEAKERS FREE SHIP , VANS MAN WOMAN UNISEX CASUAL SNEAKER SHOES CANVAS CODE AUTHENTIC VN-0 NJVLLASkechers Women's Go Walk Lite Boat Shoe - Choose SZ/Color , ASICS Womens T696n Silver/PinkGlow/ParachutePurple Running Shoes Size 9.5Skechers Women's Go Step Lite-Swerve Walking Shoe - Choose SZ/Color , New Women's Skechers 177 Retros OG 78 Vintage Style Joggers (B10)S76723 WOMEN SUPERSTAR GLOSSY TOE W ADIDAS BLUE SZ 7.5
"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."