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 Women's SONOMA SIMA Black Slip On Flats Loafers Dress Shoes SZ 5.5 , Sz 7.5 Born Brown Leather Mary Jane Velcro Flat Walking Shoes W 91597 , Women's SAS Tripad Comfort Black Shiny Leather Croc Print Slip On Shoes Sz 10.5SWomen's size 9 SKECHERS asian patterned cross strap shoes in EUCBOC by BORN Patent Leopard Animal Print Clogs Slip-on Size 8.5White Mountain New Womens Ginko Dark Brown Mules 8 M Shoes NWOBBASS Gretchen Genuine Leather Mary Jane Casual Flat Boat Shoes Women's SZ 9 1.5"Cole Haan Anjali Moc Black Leather Silver Chain Link Loafers Size 7.5 AA $175.00 , Aerosoles StitchNTurn Black Comfort Shoes Cushioned Insole Flex Sole Womens 6 M , SAS HANDSEWN WOMEN'S GRAY LEATHER PENNY LOAFERS SIZE 7.5N , Indigo by Clarks Wedge Loafer Taupe Leather 10 M , Mel Melissa Womens 39 Solid Black Peep Toe Bow D'Orsay Slip On Flat Jelly ShoeBX647 ENERGY shoes black glitter rubber women slip onBass Women’s 7.5 M Lavender Gray Mesh Summer Footwear Panama Shoes , Cole Haan Women’s Sz 8B Marlee Skimmer II Black Suede Toe Pointed FlatsNIB Women Juicy Couture Jogger Fashion Sneakers Shoes Metallic Morrison AnticsLugz Women's Regent Lo Sneaker , Dolce Vita Women's Bruno Sneaker Grey Knit Size 8.5Brooks Ariel Womens 9.5 M Silver Aqua Blue Running Shoes Sneakers Gray Athletic , Women's FABIO RUSCONI SZ.10M, ITALY,NAT/FUXIA,FLAT,RET.$160 Linden, Fashion FlatsWmns Nike Flyknit Trainer Chukka FSB Red Black Women Sneakerboots 805093-603 , AG136 LOTTO shoes purple textile leather women sneakers , ASICS Gel-Kayano 23 Sneaker - Women's Size 7.5, Blue/WhiteWomen’s Size 9 Hoka One One Pink Odyssey 2 Running Training Athletic ShoesNEW Sperry Womens Seaside Perforated Leather Slip-On Shoes Sneakers Rose BlushNike Flex Trainer 7 Women's Cross-Training Shoes size 9XS / 5 - 6 - NIKE Purple Venom STUDIO WRAP 2 Elastic Dance Yoga Shoes NEW 0000MB , ECCO Beige/Tan Athletic Shoes Womens Size 38Womens Nike Reax Rockstar White Silver Athletic Training Running Shoes Sz 8 , Women Real Leather Fashion Sneakers Sport Sandals Platform Wedge High Heel Boots ,
"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."