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.Blue nn Glitter Sexy Point Toe Comfortable Slip On Women Flats Shoes Size 6.5Clarks Collection Shoes Slip On Brown 7.5 WBrinley Co. Women's Scrunch Flexible Stretchy Side Round Toe Ballet Flats 9Ladies Spot On Formal Loafers Label F80121 , Harold Powell Made in Italy Women's Penny Loafers size 8.5B Leather Upper HV2193 , Rialto Comfort Garner Women's Loafers Black Ballet Flat Slip On Shoe Size 9M EUC , Lands End Mary Jane Brown Suede Hiking Shoes Womens sz 6 Slip-on Flat SneakerWomen's Merrell Spire Emme Black Leather Mary Jane Shoes 6.5 MMerrell Women's 7 Ballet Flat Shoes Leather Black BEAUTIFUL!!!TOMMY HILFIGER "Malenita" Black Leather Low Heel Slip On Loafers - Size 7M EUC! , Aravon Womens Oxford Size 8 B Black Leather Slip On Comfort Shoes Web 01 BKWomens Sperry Top Sider 8 M Purple Plaid Fabric Boat Shoes Leather A065 , Rocket Dog Women's Montana Garden Crochet Ankle-High Fabric Flat ShoeTALBOTS BLACK PATENT LEATHER CLASSIC POINTY TOE FLATS SPLIT SIDE SHOES SZ 6 B 6BBass x Rachel Antonoff NEW Clear Red Plastic Ballet Bowers Flats 10Chinese Laundry Womens z avalon jelly Closed Toe Ballet Flats, Black, Size 10.0Alegria by PG Lite Belle Multi Painterly Multicolored Mary Jane Shoes 35 US 5IKRUSH Women's Lou Mesh Chrome Wedge Trainers Size in ROSE GOLD Size 3Keen Red/Pink Women's Leather/Synthetic Hiking Trail Sneakers Shoes Size 6 (AV3)Nike Free 5.0 Running Shoes Sneakers Women Size 9.5 Multi Color , Women's Sneakers Hollow Breathable Hidden Wedge Loafers Casual Atheltic ShoesWomen's Nike Training Air Max S2S Mid Athletic Shoes Black/Pink/White Size 8.5 , NIB Authentic PUMA VIKKY RIBBON P White Soft Foam Comfort Insert Patent Shoe 9M , Nike Women's Dualtone Racer PRM Running Shoe, Vast Grey/Sail-Particle Rose, 8AVIA Women's Avi-Tangent Training Shoe White/Pink Scorch/Chrome Silver 7.5 W USSaucony Progrid Integrity ST 2 Walking Shoes-Women's size 9.5 White , BeBe Sport Black Silver & White Graham Jogging Sneakers Size [7.5 US] T2069 , Hoka One One CLIFTON 4 GREY BLUE PURPLE PINK WHITE US 11 & FIT MEN 9 9.5Skechers Women's Go Flex 2-INFUSE 14992 Black With Goga Max Insole , Saucony S19029-2-040 Womens Havok XC Spike SneakerB (M)- Choose SZ/Color. ,
"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."