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 Refresh Chloe-01 Leatherette Round Toe Slip On Elastic Wedge Clog Size , TS shoes TAKING SHAPE sz 6 / 37 Apollo Slides low wedge chic comfy slip-on NIB! , Women's Sequin Silver Gold Ballet Flats Dancing Shoes Sizes L & XL New , Ladies Women's Girls New Loafers Block Heel Tassel School Work office Shoe UK3-8Dr. Andrew Weil by Orthaheel Women's Evolution Brown Casual Loafers sz 8 B EUCSam Edelman Size 6 Maria Women's Metalic Gold Leather Slip On Ballet FlatsMoney! City Classified Women's Pointy Studded Trim Ballet Flats Taupe Faux Suede , MINNETONKA MOCCASIN BLACK FLATS SHOES LOAFERS SLIP ON NEW PEBBLE GRAIN SIZE 5 , Lacoste womens Raleigh Mid Hight Boat Deck Casual Shoes Sz US 6/Red , NINE WEST CELSEY RED SATIN FLATS WOMEN SIZE 6 M , MERRELL Womens Size 6.5 Qform Slip On Strap Open Back Moc Toe Shoes BrownARRAY Womens Freedom Leather Square Toe Loafers, Lime, Size 12.0 cMJhKlogs Sandy Womens Clog Shoes Display Model Leather Driftwood Smooth 8M , **Clarks Keesha Cora Loafer - Women's Size 6.5 M, AubergineSofft Somers Women’s Size 10M Black Snake Print Leather Mule Slides Flat NewConverse New CTAS Abbey Red Womens Shoes Size 7.5 M Fashion Sneakers MSRP $65 , Brooks Addiction Walker Shoes Women Size 10 (No Insole)Basket MAMZELLE ballerine compensé sandale plateform derby moc CUIR 36 NEUF , DAWGS Women's Ultralite Golf Walking Shoe White/Black 7 M US , ECCO Womens Biom Venture Low Top Bungee Walking Shoes, Black, Size 8.0FitFlop Women's The Skinny Flip-Flop - Choose SZ/color , SAS HANDSEWN WHITE LEATHER Womens 9.5 M Casual COMFORT WALKING Shoes USA MADE , Nine West Welldone Women's Fashion Sneakers Navy Multi , Nike Womens Air Max Thea Ultra Black Running Shoes Size 7 (353484)Fila J972Q Grey Pink White Womens Running Shoes Sneakers Trainers 5-J972Q-421 , Women's Asics Gel-Noosa Tri 8 Shoes Sneakers Size 9.5 Running Black White N15VANS New Authentic Slim Perf Stars Vault Lady size USA 7 , Ryka Women's Enhance 2 Cross-Training Shoe - Choose SZ/ColorTEVA Womens Willow Chukka Black Leather High Top Sneaker US 8 NEW!WOMEN'S ONITSUKA TIGER SERRANO - Brand New - FAST SHIPPING
"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."