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.Sperry Top-Sider women's gray flats size 7.5 M good shape , Naturalizer N5 Comfort Ulysses Green Woven Perforated Ballet Flats size 7M , NOT RATED Womens STELLAR STYLE Taupe Oxfords US-7; EUR-37.5 (NRFL0003-277) , PRE-Owned AK Anne Klein womens Lyndsy loafers shoes brown leather 7M Defect , CLARKS WOMEN'S CLOGS/MULES/ SLIDES SIZE 11M PRE-OWNED CASUAL SHOES COMFORTABLE , ROCKPORT..BROWN..SUEDE LEATHER..MULES / CLOGS / WEDGES..sz 10AIRIKE Women's Soft Leather Loafers Flat Slip-ONS Slippers Casual Moccasin Dr... , Traditional Indian Handmade Women Shoes Slippers Leather Flip-Flops Flat US 5-10Ryka Dark Brown Suede & Quilted Sateen Mule Clog NEWTS35 Zuly Cutout Peep Toe Ballet Flats Black , Calfskin Patent Leather Large Satin Bow Skimmer Ballerina Shoes**Sam Edelman Felicia Suede Ballet Flat ‑ Women's Size 8W BlackPleaser Round Toe Foldable Flats W/ Bow Adult Women B. Pink Pat Shoes , KangaRoos 8.5 navy blue tennis shoes pocket , DIZZY Jelly Flats Mary Janes SHOES GOLD GLITTER Slip On sz 10 M WORN ONCEAnne Klein Harmonie Navy Reptile Womens Slip-On Size 8.5MEasy Spirit e360 Pewter Snake Comfort Relenie Slingback Athleasure Sneaker 8 NewLOT OF 2 WOMAN’S RUNNING SHOES AVíA BUNDLE JOGGING FITNESS TENNIS SNEAKERS SZ 8 , New Balance 1442 Womens Athletic Shoes 7.5 B 7 1/2 White Sneakers TennisBasket Les Petites Bombes TBE P 38 A voir §§§§§§§§Nike Zoom Vapor 9.5 Tour Pink/Orange/Gray/White Shoes 631475-680 Women’s Size 7Orthoheel Melanie Black Slip On Orthotic Elastic Mary Jane Loafer Women's U.S. 7 , NEW G.H. BASS & CO Women's Shoes NAVIGATE Casual Nautical Low Top Sneakers sz 7Women's Diesel Sneakers Special Offer Athletic ShoesNike Air Max 90 Ultra 2.0 SE GS Grey Women Kid Running Shoes Sneakers 917988-004 , SKECHERS USA Inc - 13908 Skechers Go Run Bolt Womens Running Shoes Black/MultiNike Lunarepic Low Flyknit 2 Womens Running Shoes size 8 863780 500Women's NEVADOS Tan Leather Mesh Trail/Running Hiking Shoe Sz. 11 MINT! , NIKE WOMENS TANJUN ENG RUNNING SHOES (BOX NO LID ) , New Balance Women's 860V6 Purple/Lime Size 6 ,
"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."