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.Nine West Slip On Womans Shoes Size 9M Beaded *N , New Women Sandals Shoes Gladiator Flip Flops Flat Buckle Strappy Open Toe , NEW Women's Simply Vera Vera Wang Ethel Espadrille Flats Shoes all Sizes , BORN Women's Black Leather Slip On Mules Wedge Heel Shoes Size 10 MFashion Women Ballet Shoes Leisure Rhinestone Flats Shoes Princess Shiny ShoesWomens Sperry Topsider Angelfish Plaid 2-Eye Boat Shoes Size 8M Leather Upper , LN~ Born Werks -7.5 Med- Handcrafted Black Pebbled Lea Basketweave Buckle LOAFER , TALBOTS Shoes - Deep Red Crinkle Patent Leather Ballet Flats 6.5 M , Naturalizer Neman Womens Saddle Tan Leather Loafer Shoe - Size 8MCHEEKS BY TONY LITTLE WOMEN'S EASYSHAPERS WALKING MULE BLACK 7MKlogs Missy Women's Leather Clogs Display Model Shoes Tigerberry 7.5MSPERRY TOP SIDER BROWN LEATHER UPPER MADE IN CHINA SIZE 8.5 M**Naturalizer Gwen Loafer - Women's Size 9M - White , Skechers BOBS Women's Bobs Plush-Page Turner Flat Black/Multi 6 M US , 353 NEW Attilio Giusti Leombruni Marble Leather Platform Sneaker Women's Sz 38 MNew Balance 643 Womens Leather Tan Brown Hiking Shoes Sz 7 BSperry Top-Sider Women's Audrey Slip-On Flat, Size US 3.5 M,Cole Haan Zero Grand Fashion Sneakers Gray Leather Women8Medium (B, M) , Womans New Balance 574 Shoes Size 7.5New Balance Women’s All Terrain 412 Gray Purple Shoes Sz 9.5 (BWTE412N2) , Nike Women's Size 6.5 Air Max 95 Anthracite Cherry Pink Gray Shoes 336620-020Women's Orange Black Slip On Sneakers Special Offer Athletic Shoes , Women's Nike women Mon marking shoes Aesthetic Appearance Athletic ShoesWomen's Black Bow Flats Size 6 New Products Flats , [S10314-3] New Women's SAUCONY Zealot ISO 2 Running Sneaker - Navy BlueNew Balance Women's 574 Shoes Black , VANS New Authentic MG Tan MG Vault Classic Lady Shoes Size USA 7 , ASICS Women's Gel-Contend 4 Running Shoe Diva Blue/Silver/Orchid Size 8.5MNike Air Max Kantara Athletic Shoe-Women's Size 8.5, Lagoon Pulse/Lt. Blue FuryASICS Womens Gel-Kayano 23 Silver Running Shoes Size 9 (368045)
"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."