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.Covington Tan Leather Comfort Loafer Shoes Size 9.5MLifeStride Womens Valor Closed Toe LoafersBorn Concept/B.O.C. Women's Slip On Mules-Career/Casual-Black-Size 7Merrell Plaza Bandeau Expresso Women's 7 Brown Suede Mary Jane Wedge Shoes (b37) , Steve Madden Dyruss Pink satin sandals for womes. Size 8. Retail price$ 80.00 , Stuart Weitzman Womens Brown Suede Loafers Tassels Comfort Size 8 MediumDansko Clogs Shoes Mules Brown Leather Ankle Strap Buckle Womens Size 40New Women Pointy Toe Perforated Bow Tie Slip On Loafer Flat - 18051 by SBUP Line , Minnetonka Grace Moc Silver Size 7.5 New in Box , LANDS END 7.5 B Mary Jane brown suede and textile ballerina flats excellent lkn , Zara Women's Frill detail ballerinas 6446/ 101 EU39 , US8, UK6 100% Goat LeatherLands' End Pink Ballet Flats Women's 7.5B US 38 EUCONVERSE ALL STAR UNISEX CT TWO FOLD HI 136575F SHOES MEN 8US WOMEN 10US $60Fila DLS Foam Navy Blue Pink Turquoise Size 11 Running RN 91175 Cool Max Insoles , Reebok Zigtech 023501 Women's Sz 8 Pink Mesh Running Training Shoes SneakersNew Korean Women's High-top Heels Platform Casual canvas Sneakers Casual ShoesWomens Mary Jane Lightweight Mesh Elastic Sports Walking Yoga TrainersNEW CLARKS WOMENS CHEYN WALE - WOMENS SHOES - BLACK LEATHER , Dr Scholl,s American Life Collection Steady Athletic Sneakers Size 7.5 M , Nike Womens Tennis Shoes Size 7.5Women's Brooks Addiction Walker in White All Leather V- Strap Size 9 MedBaskets Femme samples shoes ETNIES VENTAGE WHITE PINK WOMEN , Women's CAPPELLETTI WOMENS Slid on 9 Surprise Athletic Shoes , Crocs Women's Sanrah Strappy Wedge Slide Sandal Black SandalsBaskets en Toile Femme US Polo Assn Rose 38Converse Chuck Taylor All Star Platform OX Black Leather SizeUS 10 Women 559016CWomen's Converse Breakpoint Pro Leather-suede Sneakers Black Sizes NIB , New Women's Skechers 13803 GOwalk Extract Walking Shoes Size 6 (Z1)*Rare* Nike Wmns Blazer High (US Size 9)Nike Tanjun Black Gold Running Shoes Youth Size 4 to 7 UNISEX New In Box
"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."