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.MINNENTONKA Woman's Size 7.5 white leather slip on shoes , WHITE MOUNTAIN "Skipper" Brown Suede Split Sole Driving Moccasins - Size 11MWomen's Genuine Leather Shoes by Clarks Everyday-Worn a Couple of Times-Sz 10 MAnne Michelle L4942 Ladies Slight Platform Slip On Shoes ~ 2 Colours Available , Ladies Clarks Flats Label - Henderson Hot , Naturalizer Womens Therese Leather Cap Toe Slide Flats , NINE WEST Women SHOES Luminarie Ballet Flat Gold Sequined Taupe SUEDE US5 35 , Soda Microsuede Shoes Size 7.5 Brand NewEileen Fisher Patch 2 Studded Flats Suede Shoes Black Slip on Sz 5.5Women's AGL ATTILIO GIUSTI LEOMBRUNI Ballet Flat Leather Shoes 6 (36) Black , Lane Bryant Size 9,11,12W Black Gold Studded,Low Heel slip on ShoesTalbots Purple Suede Leather w Cap Toe Buckle Career Slip on Flat Loafer 8.5BSkechers Sport Breathe Easy Five Star Fashion Walking Sneaker Memory Foam! , Qupid Women's Nacara-01 Fashion Sneaker Pink Size 6.0 , Nike Zoom Vomero 11 Running Shoes Women Size 9.5Saucony Jazz Original Size 8.5, Women's Running Shoes Gray & Purple. 1044 , Old Friend Alpine Slippers - Men's Size 14, Dark Brown Stony , Saucony Women's Grid Seeker Athletic Shoes Blue Size 7.5 (S15302-2) , SAUCONY KINVARA 5 RUNSHIELD RUNNING SHOES WOMEN'S 9 M RTL $100 , $99 Prince Women's Warrior Lite Tennis Sneaker Shoes, Blue/Yellow, US 8 , Fila Womens Memory Finity Running ShoeM- Pick SZ/Color.NIB Vans X Lazy Oaf Style 29 Lazy Almond Blossom Sneakers Pink Women’s Size 8 , STEVEN by Steve Madden Women's Cuddles Fashion Sneaker, Black Suede, Size 10.0New Balance Women's Nubuck 247 Shoes PinkVans CLASSIC SLIP ON Perf Leather Port Women's Shoes 5 , New Clarks 26116791 Vailee Frost Black Nubuck Women's Casual Shoes 6 USSKECHERS GO WALK 4 Women’s Athletics Shoes Size 6, Black/ Gray .....S25Reebok Womens Club C 85 EH Fashion Sneaker 6 M- Pick SZ/Color.Columbia Boardwalk Sneakers Slide on Shoes Blue sz 7 , J-41 VEGAN BLACK STRAPPY SLIP ONS SPORT SANDALS CASUAL SHOES US WOMENS SZ 7 M
"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."