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 J.Crew ADDIE BEADED LOAFERS b0421 $118 Suede upper SIZE 6Womens Ladies Slip On Sliders Diamante Slides Comfy Platform Summer Sandals SizeMerrell Plaza Mary Jane Flat Shoe Tan Brown Leather Size 8 1/2GROSBY WOMENS SLIPPERS Slip On Warm Comfortable Winter Mocassin Shoe Shoes , Sperry Top Sider BAHAMA Rose Cord Plaid Sequined Boat Shoes Sz 8-8.5 fw165 , Biala Saben Sneaker Platform Black Leather Slip On Womens Shoes Sz US 11.5Roxy Womens Atlanta Slip on Shoe Fashion Sneaker- Select SZ/Color. , MARCO TOZZI Slippers Ballerinas Court Shoes Gold NEW , SAM EDELMAN Metalic Slip On High Top Shoes Boots Booties Size 6.5 , ORTHOFEET Orthotic CHATTANOOGA MARY JANE Black Shoes Womens Size 10.5B , Converse Black Pink Leather Sneaker Athletic Shoes Women's Size US 8 , Steve Madden Womens Frederica White Fashion Sneakers 7.5 Medium (B,M) BHFO 4315 , SAS Womens Sz 11M Hope Wine Purple Nubuck Leather Moc Toe Tassel Slip On Loafer , Easy Street Women's Kila Flat, Black, 6.5 W US , Lauren Ralph Lauren Janis Slip On Fashion Sneakers, Blue Railroad , Skechers Walking Loafers Navy Blue Synthetic Women10Medium (B, M) , Skechers Women's Ez Flex 3.0 - Beautify Slip-On Shoe , Skechers Shape Ups 11800 White Athletic Toning Tone-Up Shoes Women’s Size 10 , Puma Basket Heart Copper - Copper - Womens , Womens Topshop Turin Black and Gold Metallic Elastic Trainer Sneakers Size 10.5 , Irregular Choice Oh Mama Womens Black Multicolour Synthetic & Fabric ShoesUnisex Converse Chuck Taylor CT Lucky OX - 148642C - White Blue TrainersUnder Armour Women's Fuse FST Size US 7 B(M) US Black/Glacier Gray/Penta PinkWOMEN`S NIKE ROSHE ONE NEW [511882 311] GHOST GREEN Multiple Sizes , adidas Outdoor Women's Daroga Sleek Hiking Shoe , AVIA Women's Avi-Journey Walking Shoe Chocolate Chip/Soft Coral/Snowline EcruAsics Women's Athletic Shoes GEL- FIT SANA, Pink, Size 11.5 , , Under Armour Womens - Black Running Shoes Size 10 (354103) , Nike Air Max Team ST Running Training White & Black Sneakers Shoes Womens 12Pearl Izumi Womens Black/Pink Glo Walking Shoes (34031) ,
"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."