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.New Women Qupid State-07 Faux Suede Ankle Strap Tasseled Ballet FlatEarth Shoe Pine 4 Mules Shoes Women’s 6.5 Clogs Black Leather Upper Slip On Clog , Womens Leisure Ladies Summers Ankle Strap Beach Sandals Shoes Flats Casual Sizes , MIU MIU Orange Leather Bow Ballet Flats Sz 36/6J Crew Tan Light Brown Suede Leather Almond Toe Ballet Flats Career Casual 6.5 , Crocs- Navy Blue Slip On Boat Style Shoe- Size 8 , Womens 11.5 12 42 Dansko Shyanne Black Leather Clogs Shoes Slip-On Mules Cut-Out , SOFT WALK Women's Morgan Black Slip-On Shoe SIZE 6 Amazing COMFORT! $125 , Steve Madden Eligant 6 M Gold Rhinestone Canvas D'Orsay Pointed Ballet Flats New , Naturalizer Sidney Loafers - Women's Size 10 W, Mid BrownBasic Editions Women's Mandi NAVY BLUE Mary Jane Sneaker w/ Easy ClosureGray pink color women breathable lightweight casual shoes walking sneakers , Cole Haan Country Womens 9 B Black Mules Slides Slip On Moc Shoes Air D89 , Easy Street Women's KANA Mule, Blue/Green Leaf Fabric, 8 N USNEW Nike Zoom Rival D 6 - White/Pink Running, Cross Training (Women's 8) , Womens Asics Gel Maverick 3 Running, Cross Training shoes size 11 US , Vasque Breeze 2.0 Women's Slate Brown/Red Mahogany Hiking Shoe 7.5MColumbia Dragonfly Womens Sneakers Trail Green White Beige sz 8.5 Med , Gravity Defyer G-Defy Ballistic Women's Sz 8-White Pink Athletic Shoes , Skechers Shape Ups 11800 White Athletic Toning Tone-Up Shoes Women’s Size 8.5SKECHERS PREFORMANCE WOMENS GO WALK SPORT SUPREME SHOE 14140/GYBLZoot Sports Carlsbad - Pink - WomensFILA RAY Disruptor Fashion Sneakers For Women's Shoes FS1SIA1160X WhiteNike Air Max Tailwind SZ 10 2010 Hot Pink Grey Running Shoes 415371-004 EUC G87NEW Volley THE INTERNATIONAL + 50 SHADES , New Loeffler Randall Womens Miko-Hc Cheetah Fashion Sneaker Size 9.5Brooks Ghost 6 Neutral Running Shoes sz 9M, 40.5 EuroNew Under Armour Kick Sprint Spikes Womens Size 9.5 Venetian Blue , adidas Originals Women's ZX Flux W Running Shoe, Grey, Size 11.0Skechers Women's Synergy Algonac Work Boot - Choose 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."