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.Lilly Pulitzer for Target Size 8 1/2 Espadrilles , NWT, Multi-color Great Buy , A. GIANNETTI md ITALY BLACK SUEDE & WHITE LEATHER TRIM 1.5" FLATS SZ 39-10 , Comfortable White Dove Woman's Size 10 Beige Ballet Flats , Women’s Merrell Light Brown Perforated Textile Ortholite Clogs Shoes Size 6 , Womens Shearling Lined Sperry Top-Sider Leather Loafer Shoes 7M , Gold Shimmering Open toe Sandals Mule Heels Slip on Women's party shoes , Marc Fisher Stormy Cross Strap Ballet Flats, Dark Green, 6.5 US , Euro Soft Audie Black Leather Oxford loafer Comfortable Conservative nice $89 6 , Dansko Women's Black leather Low Wedge Open Back Clogs Size US 8 , CECILIA BRINGHELI Striped Canvas and Leather Flats -- Size: 37 (EU) -- NWOBNEW Sperry Top-Sider Animal Print Bow Boat Shoe Loafers Flats Size 7 , Tommy Hilfiger Womens Beau Almond Toe Slide Flats White Size 7.5 , NEW BALANCE "WLD5000O" ATHLETIC SHOES WOMEN SIZE US 10.5 med NEWwomens size 8m NIKE 510790-060 LUNARSWIFT-4 GREY FUSCHIA RUNNING SHOES EUC L@@K , Skechers Womens Bobs Ballyhoo Olive Size US 6 TT25 34960New Womens Skechers GoWalk 2 Shoes Style 13590 Size 6 Black 129A sr , Vans Women's Prison Issue 2 Tone Leather Double Velcro Sneakers Sz 10 NEW , Women's Chaco Hiking Trail Shoes Brown leather Canyonland Low Event Sz 7.5Women's Walk Reebok Size 8 1/2 N White Tennis Athletic Shoes Air TransmissionNike Lunarglide 3 Women's Running Shoes Silver/White 454315-017 SIze 9.5 US , Stuart Weitzman Black Leather Studded Pull On Sneaker Booties Size 7.5M , Womens Girls Creeper Shoes Platform Hot Sale Round Toes Slip On Athletic Sneaker , Women's SBENU Womens Premium Sprots Sneakers Moderate Price Athletic Shoes , Women's women's sneakers Ryka size 10W Quality Athletic ShoesSkechers Sport Women's Energy Sneaker White/Millennium 8 M US , Reebok Classic White Running Shoes w/ Pink Accents Women's Size 8.5 M / 39 EuroNike Air Max 95 Premium Special Edition Rare Athletic Running ShoesASICS Womens Gel Flux 3 Running Shoes Blue Green Sz 9 , New Balance Women's 450v2 Running Shoes, W450SL2 Silver/Salmon/Blue Size 9.5 , SKECHERS STREET LA Women’s Athletics Shoes, Gold, 6 Eur 36. ....S38
"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."