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.Cole Haan Women’s Sz 5B Black Leather Tasseled Loafers Deck ShoesSALE Ladies Savannah Slip On Mules UK Sizes 3-8 F0760 , BASS "Tenton" Brown Suede Slide On Open Back Slipper Shoe- Size 8.5 M , Womens sz 9 N Proxy teal suede bow ballet flat shoes pump slippers slip-on dressARRAY Womens Breeze Leather Closed Toe Ankle Strap Loafers, Navy, Size 11.0 Bk7g , Crocs Womens Sz7 Fuax Fur Lined Mules Shiny Blue Midnight Dream S5 ClogsNIB Mennetonka Moccasin Britt Trapper Womens Mocs/Loafers 5 ChocolateLuxe Australia Collective Loaf Sand Leather Shearling Slip-Ons Woman's Size 6Marc Jacobs Womens Ballet Flats Size 38 US 8 Beige Black Satin Leather , WOMENS FLOSSY FLOSSYS SLIP FLAT CANVAS PLIMSOLL PUMPS TRAINERS SHOES SIZES 2-9Ecco Oxblood Mary-Janes Women's 8.5 Medium Flats , Crown Vintage Womens Telian Leather Closed Toe Loafers Taupe Size 6.0 WfeBK-Swiss Shock Spring Women Sz 11 Leather Pink Gray Cross Training Tennis Shoes , Women's Hiking Outdoor Shoes Trail Trekking Sneakers Breathable Climbing ShoesNEW Skechers Performance Ladies' Go Step-Lite, Flats Black/GREY Select Size.Chinese Laundry Women's Gracias Ballet Flat, Hot Pink/Metallic, Size 6.5New Balance womens 1765 size 9 running walking crosstraining no insolesVolley International Womens Casual Sneakers Yellow Blue size 5,6,7,8,91806 Nike Benassi JDI Men's Slides Slippers 631261-403Clarks Walking Trainers women's size 7.5 M US/ DNIB UNLTD BY MARC ECKO PHORTUNE SNEAKERS SKATEBOARD BLACK WOMENS 6Merrell Womens Walking Shoes Size 9 (387)Sperry Orange Gray Tennis Sneaker Athletic Running Womens Shoes Size 10 MNIKE DUAL FUSION ST 2 UNIVERSITY BLUE Size: 5.5 WOMAN NEW RUNNINGConverse Women's CT II Hi Top All Star Sneakers Black Black/White Size 7 MAsics GT-2000 Black Running Shoes Women's US Size 10 (C3,20) , Womens Reebok ROS WORKOUT TR 2.0 TRAINING SHOES AR0538 AR3207 NEW , Saucony Women's Hurricane ISO 2 Blue/Silver/Citron S10293-1 , New Balance Flash V1 Running Shoes Womens Size 8 , Steve Madden Womens Ecentrcg Sneaker- Pick SZ/Color. ,
"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."