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.Volcom Soul Mates Black Women's Shoes Size 6.5RUDOLF DASSLER BY PUMA RHYTHM ULTRA LIGHT Ballerina Ladies Shoes Mink/Navy 7LADIES SPOT ON CANVAS BOAT SHOE IN YELLOW, WHITE, NAVY STYLE F8724Tahari Womens Esther Black Suede Dress Flats Shoes 5.5 Medium (B,M) BHFO 8314 , Bass - Anita Size 7.5 M Brown Suede Slip on Women's Shoes , Vince Camuto Gold Leather Espadrille Flats Womens Shoes Sz 12 , Easy Spirit Women's 5 1/2 M Brown Patent Leather and Mesh Low Heel Slip On ShoesLifeStride Women's Fantell Ballet Flat Lux Navy Size 6.0Womens Shoe Soda Display Open Toe Sandals Light Brown *New*SAS Tripad Ivory Size 7M Slip-On Loafer Shoes , Skechers BOBS Womens Luxe Bobs-Big Dreamer Flat- Select SZ/Color. , Sam Edelman Jones Contrast Penny Loafer, Pink/Orange Size 6 NEVER WORN , Isaac Mizrahi Dannie Navy Blue Leather Bow Ballet Flats NEWWALDLAUFER Women's Oxford 319881 BLUE Oxfords. US size 8.5. Free shipping! , Born Concepts Brown Faux Leather Clogs Mule Slip On Shoes Step In Mules Buckle , Everlast? Women's Martha Athletic Shoe White Wide Width 7.5 US , Nike WMNS DUNK SKY HIGH SKINNY WHITE-MED GREY-SUNBURST LEOPARD SZ 8.5 SHOE , Cole Haan Air Tali Bronze Brown Shimmer Leather Wedge Heel Shoes Women's 7.5 BCalvin Klein Sally White Womens Shoes Size 6.5 M Fashion Sneakers MSRP $98 , Women’s Nike Free TR Fit 3 Breathe Athletic Shoes Size 8.5B Multi-Color , Avia Avi Union A1439W-BSV Black Synthetic Leather Shoes Medium (B,M) WomenATHLETIC WORKS WOMENS ATHLETIC SHOES SIZE 7 COLOR BLACK GREEN LADIES CASUAL SHOE , Women's 23475 Black Kindred Skechers Utmost In Convenience Athletic Shoes , Women's crocs Womens - Pick SZ/Color. Fine Workmanship FlatsWomen's Micheal Kors Flats Online Shopping Flats , Merrell Ladies Trainers (Avian Light) LEATHER BRACKEN to 4.5 (GO) , Cute Cockatoos Parrot Running Shoe For Women- Free Shipping , Nike Women's Orive NM 677136-001 Athletic Shoes Size 6, Black 625 , Skechers Performance Women Go Run 400 Obstruct Size 10 Gray BlueSaucony Hurricane Blue/BabyBlue Running Shoes Women's US 7.5 (Q1,16)
"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."