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.Bjorndal Berkley Women's Suede Brown CLOGS Size 11 DLadies Crocs Pomegranate/Raspberry Shoes Style KADEE SNAKE PRINT FLAT WOMENPineapple Espadrilles Flat Slip On Summer Womens Girls Pumps Plimsoles Shoes , Simple Women's Size US 6.5/Black Buckle Loafers Shoes - Free Shipping!Nine West Womens Stefany Leather Pointed Toe Slide Flats, Red su, Size 5.5 VZyuSAS Siesta Burgundy Leather Slip On Moc Toe Loafers Flats Shoes Womens 8S , Walking Cradles 7.5 WW Red Clogs , LAUREN Ralph Lauren Janis Loafer, Women's Size 5.5, WhiteWomen's Allen Edmonds Helena Pink Breast Cancer Ribbon Shoes Size 10.5 M NEW , Oka B. Annabella Oka B Blush Womens Ballerinas Size 7MDr. Scholl's Womens wander up Closed Toe Loafers, Black, Size 6.0 ig7J , Lady Riddell Pro Escape Women's Mid-Top Sneakers White w/Teal New Old Stock Sz 7Vans Aubree Womens Skate Shoes Size 9.5 Black White Checker Classic SneakersSkechers D Lites Life Saver Waking Shoes-Women's size 8.5 Black , Caterpillar EXACT Womens Grey P90789 Suede Mesh Steel Toe Safety Work Shoes , LAUREN Ralph Lauren Janis Sneaker, Women's Size 8 B, Blue , Women's Betsey Johnson Women's Hazyl Flat Exquisite (in) Workmanship Flats , Skechers 21139 Sport Womens Verified Fashion Sneaker- Choose SZ/Color. , Sperry Size 7 Wild Rose Boating Sneakers New Womens Shoes , Womens Nike Classic Cortez Grey Persimmon Nylon Suede Size 10 487647 001 , Keds Women's Coursa Knit Fashion Sneaker - Choose SZ/ColorSkechers Performance Womens on-the-Go Glide-Sprint Walking Shoe- Pick SZ/Color.Sperry Top Sider Women 9265976 Brwn / Prpl US Sz 6 M - FREE SHIPPING - BRAND NEW , NEW PUMA womens FENTY RIHANNA creeper bow sneaker sandals PINK size 9.5New Balance Women's Vazee Verge V1 Track Shoe White Munsell/Flame Size 12.0The North Face Womens Ultra 109 GTX Athletic Mesh Trail-Running Shoes Size 8.5 , Under Armour Thrill 3 Women's Running Shoes 1295770 962Under Armour Womens Street Precision Slip On Color Blocked Sz 9.5 Blue Aqua , Skechers GoRun Lightweight Running Shoes Sneakers Womens 5.5 Breast Cancer Model , B0 Auth NIKE AIR Pegasus 92/16 Print Black/Grey/White Shoes 844927-001 Size 7.5 ,
"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."