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.Liz Claiborne Flex Carrie T Strap Shoes Leather Medium Wedge Heels Pink Sz 6.5 , Sperry Shoes 9M Black Moccasin Croc Print LeatherDexter Black Shoes Loafers Slip On Comfort Shoes Size Womens 6 WideMERRELL PLAZA BANDEAU DARK TAUPE LEATHER MARY JANE WEDGE SHOES WOMEN'S SIZE 8.5Easy Street Women's Effie Flat, Silver/Metallic Wash, Size 10.0Women's Lands End Leather Shoes Slip-on Casual Mocs Casual Comfort BEIGE-10 B , Frye Black Leather Ballet Flats US Size 7 , Womens 9 M Indian made in Canada metallic pewter gray leather moccasins fringeSperry Top Siders Womens 7.5M Vintage Boat Shoes Gray Neon Green Leather P109 , EUC Weekend Barber Shoes Women Leather Shoes Sz. 39 8 Beige Silver , NEW Ivy Kirzhner Heartbeat Mules Size 7.5 Heart Gold Leather , Nine West Womens Sign me up Leather Closed Toe Ankle Wrap Slide, Black, Size 9.0BORN BLACK SUEDE SLIP ON WEDGE WOMEN SZ 11 MSalvatore Ferragamo Studio Womens Black Loafers Slip-On Dress Shoes Wmn 7.5 BSteve Madden Twynkle Women's Taupe Studded Fashion Sneaker 6.5M , Women's Nike Air Pegasus 29 running shoes sneakers size 8.5Asics Womens 8.5M Gel Venture 4 T383N Athletic Training Running Shoes Grey Green , GALA-3-40 WOMEN SUEDED PEEP TOE CUT OUT BOOT ELEGANT BLUSH , Vans Women's Alpaca Ankle-High Leather Slip-On Shoes , Healthy Comfortable Hemp Jute Slippers Flip Flops Thongs - men,brown , 1 x HOLDEN Mens Grosby SCUFF BLACK Slippers Slip on Home Slipper Warm Car RevSuperga Burgundy Tennis Shoes Women’s US Size 6.5Women Chic Sequins Creepers Wedge Heels High Platform Shoes Black White Sneakers , Lands End Womens Hiking Walking Water Resist Boots Shoes Size 7Penny Loves Kenny Women's Arty V Sneaker, Wine Velvet, Size 9.5 p2BQ , ADIDAS WOMENS ORIGINALS STAN SMITH SNAKESKIN PRINT LIGHT ONIX/WHITEWomen's size 9.5 Medium New Balance 560 LS7 Women's Running Shoes SneakersSkechers Sport Women's Flex Appeal 2.0 Insight Sneaker,White/Silver,9 M USNIKE WOMENS HAKATA RUNNING SHOES #AJ888-003 (BOX NO LID)Salomon Sense Pro Women's Lotus Pink/White/Melon Bloom Trail-Running Shoes 8.5M
"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."