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.LL Bean Women's Olive Suede Skimmer Slip On Shoe 9 M B Excellent Condition! , Women's Bamboo Shanta Ballet Flats White Synthetic size 6.5 New without BoxBorn Orange Leather Slip On Mule Clogs Women's Shoe Size 7 SlidesLizsport By Liz Claiborne Black Fabric Walking Shoes Open Back Size 7 M , SPLENDID STRAPPY WEDGE SANDALS BLACK CORK WEDGE HEEL SIZE 7.5ZARA JEWELED SATIN PINK SNEAKERS SHOES SZ 37/7COLE HAAN G Series Brown Leather Driving Loafer Stitched Design Size 6 1/2 B , Jeffrey Campbell NWOB Women's Pink Purple Multi Embroidered Slide Flat Shoe 8Tods Womens Bright Red Suede Slip On Silver Tone Driving Loafers Size 6.5 , DANSKO Professional US Black Leather Slip On Clogs Nursing Shoes Sz 38 US 7.5-8 , Nine West 25029843 Womens Maudisa Suede Loafer Flat- Choose SZ/Color. , NEW STAR Women Outdoor Sneakers Fashion Comfortable Black Shoes 4556 e_CAerosoles Womens Fun Fact Fashion Sneaker- Pick SZ/Color.Dark Brown Patent Leather BRIGHTON Tamyra Criss Cross Strap Backless Heels 9 M , Women’s SIZE 9 ASICS GEL-CUMULUS 17 Running Shoes , Crocs Women's Swiftwater Cross-Strap Slip On - Choose SZ/ColorNew New Balance Womens 555 Blue Walking Shoes Size 5.5Sperry Top-Sider Women’s 9278136 Blue/White Stripes Canvas Boat Shoe Size 10MCLARKS SPRINGERS Women US 6.5M Brown Leather Fashion Sneaker casual Slip OnSkechers Flex Appeal 2.0 in Code Hi Top Sneaker, Women's Size 8, Grey , Skechers Sport White D'Lites Memory Foam Athletic Shoes Wmn's Sz 6 M / 36 EU , Women's Brooks Ghost 5 Shoes Sneakers Size 10B Running Black Purple White AA9Brooks Ghost 9 Running Shoes Womens Size 9 B Silver BlueU.S. Polo Assn.(Women's) Women's Cece Fashion Sneaker 7 M USWomen's Xtratuf Women's Riptide Water Shoe Elegant Appearance Athletic Shoes , Women's ZARA PRINTED LOAFERS (US5-11) [ref:7572/301] Fine Workmanship Flats , Skechers Women's Go Golf Birdie Shoe - Choose SZ/Color , Nike Shox Air Zoom Diana Taurasi [314037-102] Womens Basketball Shoes Sz: 7Superga 2750 Velvtw Blue Womens Shoes Size 9 M Fashion Sneakers MSRP $119 , Converse All Star Women’s Metallic Rubber Sneakers!! New!! Msrp. $75.00 Sz. 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."