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.J CREW TOPSIDER FOR J CREW 2 EYE BOAT METALLIC LEATHER SHOE SIZE 9SOLDES femmes marron à enfiler CROCS semelle compensée (US 10) Lexi , DANKSO SZ 42 US 11.5-12 TWO TONE BROWN AND OLIVE SUEDE LEATHER CLOG MULES SHOESTalbots Canvas Bow Round Toe Ballet Flats Slip Ons Women's Size US 6AASAS Loafer Women size 6 m Black Leather , Rieker Sportlich Long Wing-Tip Women's Brown Leather Oxfords Shoe Size 6 (DA4)New Balance Women's WX623AB2 Black Cross Training 11 B NWD1095 , NIKE Women's Free 5.0 TR Fit 5 Training Shoe Running Sz 11 , Reebok Your Flex Micro Web Pink Navy Blue Athletic Running Shoes?Womens Size 9Women's Casual Running Athletic Shoes Fitness Sneakers Traveling Breathable Girl , Sugar Womens Granita Low Top Slip On Fashion Sneakers Black Size 8.5Converse All Star Shoes Size 9.5 , Skechers Womens Fresh Start WhiteSilver Running Shoes Size 9 (326462) , Saucony Triumph-9 Women’s Sz 8 Everun “Silver & Pink” Running Shoes SneakersWomen's Converse All star Bright Neon Green Canvas Low Top Unisex Sneakers Sz 5 , Nautica Long Bay Slip On Fashion Sneakers 277, Black Denim, 8.5 US / 39 EU , Woman's Pink and Black Water Shoes by Zone Pro - Size S(5-6), M(7-8) or L(9-10) , Ahnu Women's In Studi-Om Yoga Shoe , Brooks Addiction Women Running Shoes Size 9.5 E Grey Teal Silver Sneaker S07 , Lauren Ralph Lauren Women's Cedar Fashion Sneaker Persimmon Size 8 B New , NIKE Air Max Tailwind 8 Women's Running Training Shoes- 9 worn 3xWomen's Nike Lunarstelos Black Metallic Silver Anthracite White 844736 001Skechers Earth Fest Upcycle Slip-On Women's Shoes , NEW COLE HAAN WOMENS WOMEN'S GRANDPR? TENNIS SNEAKER - BUFFALO PLAIDConverse One Star Ox Women's Pure Platinum 159710CNike Womens Roshe One Training Running Shoes Sea Coral Pink White Size 8 NEW , New Balance 812vw Women WW812vw Walking Shoe sz 12 wide , NEW Under Armour Womens Glyde TPU CC SOFTBALL CLEATS Blk/Wht/Slvr 9.5 FREE SHIP! , Woman’s Nike Free TR Fit 5 Black White Gray EUC Sz 11 704674-004 5.0Womens Merrell Smoke Leather Hiking Trail Shoes Brown Grey Size 7 / 37.5 ,
"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."