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.New New Angel Hot Pink Metallic Vegan Ballet Flat Women's Sizes 7 1/2, 9Women's, Maui Island Boat Shoes, Jiffy, US 8.5MCult Women's Classic Red Canvas Flat 37EU/7MSkechers Cali 36674 Women's Pink & Brown Canvas Slip On Sneaker Shoe 8.5 MSam Edelman Bev Women's Beige & Black Leather Slip On Ballet Flats Shoes US 9.5Easy Spirit Leather Navy Blue Slip On Loafers Women's Shoes Size 8.5Women's Sperry Top-Sider Sequins Pink White Size 6 9826751 Boat Shoe Ribbon , Croft & Barrow women’s Ortholite cut out ballet flat 8 M USA , Duck Head Size 7 1/2 WW Judy Shoes - MahoganySalvatore Ferragamo Women Shoes 9 4AWomen's Tesori Beige/Black Espadrilles Size 8.5 MSpring Step Hearts Mary Janes Bronze Size 41W (US:9.5-10)Sas Tripad Comfort Me Too Black Leather Slip On Double Strap Loafers Shoes 11 MDC Evan HI TX SE Blue/Brown/White Skate Shoe 7M , Women's FILA Athletic, Workout Sneaker Shoes Size US8 UK5.5 , THE NORTH FACE Ortholite GRAY Suede SNEAKER Walking HIKING Sport OXFORD Women 10 , Nike Air Shoes Women’s Size 6 , Skechers Womens Go Vulcanized Strand 13732 Sneaker Shoe , FRANCO SARTO Brown Work Career Dress Shoes Women Size 8.5 RandyChinese Laundry Womens EASY DOES IT Suede Pointed Toe Ballet, Blue, Size 7.5 64QCharlotte Olympia Womens Single Flat Shoes Cat Mask Size 35 5 36 6 Lot 6 LL19LL , Black Stretchy Woven Fabric BERNIE MEV Mary Jane Wedge Style Shoes US 7.5 - 8 , Betty Boop Milkshake Kicks Collection Sneakers Women Size 10 Euro Size 42.5LE COQ SPORTIF Deauville Plus M Satin Women's Shoes , Adidas Originals Women’s FLB Flashback St. Major Olive Green Off White Size 7 , Puma Fenty Rihanna Bow Creeper Sandal Oatmeal Platform 7 7.5 8 $140 C126-128adidas ZX 700 - Grey - Womens , CONVERSE ALL STAR CHUCK TAYLOR SEQUIN OX GUNMETAL GLITTER SIZE 7 WOMENREEBOK FREESTYLE HI COLORS LIME GLOW GREEN WHITE WOMENS SIZE SNEAKERS BS9369Womens Rocket Dog Casual Fashion Denim Sneakers Size 8
"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."