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.PATAGONIA - SPORTY SUEDE SLIP-ONS BALLET FLATS - DOVE/LLAMA BROWN - LADIES 8Qupid Women's Bee-53 Ballet Flat, Blush, Size 7.0 vf4vSanuk Hemp Olive Green Espadrille Hard Sole Slip On Womens 8 Mens 6 , JIMMY YOO EMBROIDERED CANVAS WOMEN'S SNEAKERS SIZE 5.5 , New Women's Stylish Almond Toe Buckle Zipper Low Heel Booties Shoes Size 5 - 11BORN Size 6-6.5 (37) Green Suede Leather Tasseled Low-Backed Slip-Ons Loafers , JIBS Suede Rubber Soles Slip-On Winter Snow Drawstring Clogs Mules Women's US 8 , Women's Prima Royale Tan Suede Oxford 7M, Clean!! Gently worn!!Women's Sperry Top-Sider Brown Multi-Colored Canvas Boat Shoes US 8.5 MFranco Sarto Snake Print Flats Womens Synthetic Size 10 Bow Front Grey -6270 , LifeStride Women's Motorway 2 Flat, Mushroom, 9.5 W US , Vionic Orthaheel Size 10 Wineberry Mary Jane Flats New In Box Style 25Elisa7.5 M Nine West Women Palyla Synthetic Walking Shoe Sneakers White Sparkle Gold , Kork-Ease Women's Nessa Orange Leather Flat 7.5MAnkle Strap Pull On Womens Ballet Flat Pull On Chic Flats Autumn Shoes All SizesNEW Club Santoni Made in Italy Loafers Fabric Upper Leather Trim Lavender Sz 37NIKE INITIATOR Running Walking Tennis Shoes Hot Light Pink Grey Womens Sz 6.5 , RYKA Glide Walk Leather & Mesh Black & Pink Sneakers Womens Shoes Size 10MWomens Gray & yellow NIKE LIVESTRONG Shox Athletic Sneakers Shoes Sz 8Asics 39.5 8.5M Gel-Scram black neon pink blue running womens tennis sneakers , Ryka Womens Dash 3 Navy/Pink Walking Shoes Size 10 (28853) , Reebok Women's Athletic Shoes White Lite Rush Performance Active Wear Size 11 US , Fashion Mens Women TRAINERS Flats Sneakers Running Leisure sport Casual ShoesNEW Nike Womens Nike Free TR 6 - White Running, Cross Training (Women's 8)Vince Camuto Bretta Leather Perforated Mule Sneaker BLUE NOTE 7.5M NEW IN BOXHigh Quality Trail Running Shoes For Women Cushioning Breathable Outdoor Sneaker , Brooks Pure Drift 2 Womens 7.5 Med Shoe Running Athletic Sneaker Black Pink GrayNEW Skechers 8.5 Tan Stone Go Walk 3 Performance Slip On Shoes Goga Mat 13980NEW Vibram Fivefingers Classic SmartWool Womens Size 36 37 $85 WS102Asics Gel-Kayano 21 Women's Sz US 8 M Blue White Pink Running Shoe Dual Max IGS ,
"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."