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 Womens S.O. TURNER Gray Slip On Flats Fashion Loafers Dress Shoe sz 6 , Cole Haan Slide Sandals / Heels, #D12713, Brown, Womens US Size 8 , J CREW FOR SPERRY TOP SIDER BLUE BOAT SHOES SIZE 8.5 women03-128 Steve Madden Sinna (Black) Women's Slip on SIZE 6MINNETONKA 9.5 MULES FALL IT ITEM! SLIP ON BLACK LEATHER TOOLED WESTERN DESIGNER , Naturalizer N5 Comfort Black Leather Woven Ballet Flats Womens 7.5 ShoesBeacon Womens Picnic Closed Toe Espadrille Flats , NWT $65 Propet Womens Morgan CIGAR Microsuede Slipper Shoes 6.5 Medium (B,M)Red Hat Society Women's Jazztime Red Leather Shoe Size 8.5 M Grasshopper Keds , Women's Shoes Bamboo Chantel 30V Casual Ballet Mary Jane Flats Light Taupe *New*GRASSHOPPERS BY KEDS WINDHAM CANVAS SLIP ON NAUTICAL SHOES SKIMMERS BLUE Sz 10 MMarc Fisher Womens Black Loafer Flats Leather Studded 8 M Shoes , Earthies Luma Pewter Laser Cut Leather Hidden Wedge Loafers, Women's US 9.5 BBurlesque L'Artiste Collection By Spring Step Womens Sandal Red Multi US 7 , Clarks Navy Blue Leather Gracelin Mara Slip On Comfort Ballet Flats NEWSpenco Womens Siesta Canvas Orthotic Slides - Pink , $69 Khombu Womens Ashley All-Weather Sandal Shoes, Grey, US 10Women Genuine Leather Round Toe Rabbit Fur Mules Flats Oxfords Buckle Warm Boots , SANUK WOMEN GILDED GIRL T-STRAP TAN THONGS SANDALS US 6 / / NWT , TRETORN ECO ORTHOLITE TENNIS CANVAS SNEAKERS US SIZE 5.5 AND 6 CONVERSION CHARTVtg 90s Signed Tommy Hilfiger Leather Tops Black/Pink Women size 8M. LOGO FLAG , Clarks Womens Black Leather Tennis Shoe Sneaker Size: 11M EU: 42.5 UK: 8.5 , Steve Madden Brown Slip-On Sneaker SZ 7 MINT!Merrell Capra Bolt Women's Bright Red Hiking Shoe 9M , MERRELL Performance Women's Black Suede & Faux Fur Walking Shoes 7? MWomen's Cheer shoes size 7 Goods Of Every Description Are Available Athletic ShoesSuperga 2750 Cotu Mens Womens Black White Blue Canvas Trainers Shoe Size , Palladium Women's Aventure Textile Ankle-High Fashion SneakerMBT Chapa Stone Walking Toning Rocker Shoes Womens Sz 8.5 M Tan Leather Sneakers , Skechers Women's Bright Idea Fleet Footed Gray 23603/GRY
"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."