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.9 M USGI Women's US Military Shiny Black Uniform Dress Shoes Honor Guard , Nine West women's loafer brown leather heeled size 8.5 , Original MOLA Womens Mary Jane Shoes Handcrafted S. America Imported Sz 5.5 , Drew Desiree Brown Nubuck Leather Mary Jane Shoes Women's 6.5 Medium 14385-06J. Loren Suede Leather Upper & Lining Casual Loafers Shoes 490-40 Size 10 1/2 41Prego Black Suede Silver Tone Grip Sole Loafer Flat Estimated Size 37.5MERRELL 37 / 6.5 Moc Moccassin Black Suede Leather & Wool Top Ortholite Qform , TORY BURCH ballet flats Lot Of 2 sz 6.5 FREE SHIPPING , VANELi Women's Liddy Black Leather Slingback Pump , Superga 2750 Linu Fashion Sneakers Women's - Ecru S001W30 912Marc Jacobs Womens Satin Metallic Trim Loafer Espadrilles Flats BHFO 5282 , **Cloudsteppers By Clarks Sillian Bella Casual Shoes - Women's Size 8.5 N - NavySteve Madden Quilted Wedges Size 8Women Mesh Sneakers Tennis Comfortable Walking Athletic Shoes Ultra Light WeightG by Guess White Leather Sole Sneakers Shoes Womens Size 7-1/2 7.5 M , Sperry Cormorant Slip-On Duck Shoe - Ivory & Cognac - 5M - NWB - 100 , Lucky Brand Womens EMMIE Leather Closed Toe Ballet Flats, Black, Size 9.0 27s5 , DANSKO ANIMAL PRINT SLIP ON SHOES”WOMENS LEATHER UPPER SIZE 37MAdidas FALCON ELITE 5 Breathable Mesh Lightweight Running Shoes Black Sz 8-M , roman womens buckle strap hidden med heel creeper zip platform shoes sneakersLacoste INNO 507 Womens Size 8 Strap Black Yellow Slip-On Sneaker F9ASICS GT 2000 Women's Running Walking Shoes Black Gray Purple Size 8 T3Q6N , DRAVEN 'SKULL & GINGHAM CHERRIES' SNEAKERS WOMENS MANY SIZES NWT SLIP ON CANVASJellypop Women's Dallas Sneaker Natural 10 B(M) USWomen's minnetonka moccasins size 6 Quality Superior Flats , Skechers BOBS Womens Phresh - Top Spot Sneaker- Select SZ/Color. , ECCO Womens Gillian Low Top Pull On Fashion Sneakers, Vanilla, Size 8.0 vvwyBrooks Women's Adrenaline GTS 16 Running Shoe 9.5 M Black , New Balance Revlite 247 Women Sneakers Running Shoes WRL247SQ Size US 7 NEWWhite Mountain Women's Sutton Criss Cross Slide Olive Suede Heeled Sandals ,
"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."