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.Merrell Mimosa Cord Black Suede Leather Bungee Flat Casual Shoes Women's Size: 7New Round Toe Causal Silp On Faux Suede Strap Buckle Padded Womens Flats ShoesEasy Spirit Women's Black Flats Leather Slip on Shoe Size 9 ✞ , WOMENS CUT OUT LADIES GEEK T-BAR GIRLS OFFICE SCHOOL PUMPS SHOES SIZE 3-8G. WIZ Block Party Cognac Brown Soft Leather Loafers Driving Shoes 8.5M 281785 , B.O.C Womens Size 7 Flats Cheetah Print Shoes Animal Print Born Boc , Kalso Earth Women's 6.5B Ivy Mary Jane Shoes Leather Almond , Franco Sarto Samanta Studded Backless Loafers, PinkEasy Spirit Women's Black Kable Cap Toe Slip On Flat Shoes Ret $79 NewLadies Genuine Real Leather Tassel Front Comfortable Women's Loafer Flat Shoes , New Gray Patent Leather & Textured Nubuck Leather CLARKS Neenah Gardens Flats 9 , NEW Clarks Slip-on Loafers - ASHLAND BUBBLE - BLACK SNAKE - 9 M , Clarks Sillian Jetay Slip On - Women's Size 7W - Pewter , Mizuno Women's Wave Lightning Volleyball Flat Shoes Size Us 8 / Eu 38.5 Black , La Redoute Womens Sling Back Ballet Pumps With Sparkly Heel , Apex Women's Brown A201 Eveyln Loafer FlatSUPERGA Sneakers Navy Blue Unisex Canvas Shoes Women’s 10 / Men’s 8.5Nike Air Max White Pink Silver 3088888340 061 Size 8.5Nike Shox NZ Running Shoes 366571 Womens Size 9.5 Grey Black Neon Green , RARE VTG 1990's OG Reebok Insta Pump "Above The Rim" Basketball Shoes size 7.5Merrell Women's Aqua Moc Water Shoes Slate Blue Gray 9.5 MWomen's Ryka Memory Foam Size 9 Easy-to-clean Surface Athletic Shoes , ADIDAS WOMENS SUPERSTAR WHITE/CHALK CORAL CG5462 , 2008 Womens Nike Reax Run 8 White/Orange Running Shoes! Size 9.5 $120.00Merrell Running Shoes Sz 11 Women Purple Granite NWOT YGI E8Five Ten Guide Tennie Stone Grey Women's 10.5 , OLUKAI PRE-OWNED 20195 WOMEN'S KAMIKI SYNTHETIC TRAINER SNEAKER SHOES US 8Converse Women's SZ 8.0 M Shoes Midnight Navy/Barely Volt 557910F PRE OWNED 8452Women's Asics Gel Dedicate 4 Preowned Tennis Shoe Size 8.5Women's Shoes High Top Fashion Sneakers Fur Lined Winter Warm Ankle Boot Buckle ,
"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."