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.City Classified COMFORT SHOES WOMENS SIZE 6 WIsaac Mizrahi Live Imfrankie Womens Black Suede Shoes size 6 M , Jambu Regatto Sport Ballet Flats 560, Gray, 8 US , NEW Circus by Sam Edelman Banks Black Sparkle Ballet Flat Sz 7.5M Ret $80 , TALBOTS NWOB Tan ALL Leather~ 7 M~ Moc Croc Tassle Loafers Italian Shoes Womens , Sam Edelman Becker Orange Navy Blue Women's Slip On Loafers Flats Size 8 MAnne Klein Womens DANEEN Leather Square Toe Loafers, Navy, Size 5.0 dzDj , GUC DVF Diane von Furstenberg ballerinas Flats fabric printed Red white size 10Marc Fisher Women's Alen Mary Jane Flat, Grey, Size 8.5 , Fila Stellaray Women's Silver/Blue Sneaker 6.5MWomens Get Fit Gym Mesh Walk Go Running Shoes Athletic Sport Run Sneaker US 5-10SKECHERS Air-Cooled Memory Foam Slip-On Sneakers/Shoes--Gray--Size 7.5 GREAT!!Asics Gel Venture 4 Gray Purple Running Shoes Women Size 9 SH1 , Aldo Womens telassi Closed Toe Mules Black Size 8.0 M6XBSaucony Grid Cohesion 7 Athletic Shoes Size 8.5 Sneakers 15181-2 Pink Gray , Womens - NIKE FOCUS FLYKNIT - Gray Athletic Active Shoes White Melon Wolf US 7Womens MERRELL MESA VENTILATOR Blue Gray Hiking Shoes Size US 6.5 M (b31)Mizuno Womens Size 10W Shoes Wave Alchemy 9 Athletic Running Cross Training EUCAvia Avi Solstice Womens Black White Athletic Running Sneakers ShoesWomen's keds shoes size 6.5 Year-end Bargain Sale Athletic Shoes , IIJIN Python Pattern Vegan HT Sneakers For Women's Size EU-39(US-8.5) , adidas supernova glide 8 w - Grey - Womens , Brooks? ~ PURE CADENCE 5 Run Shoes ~ 1202151B499 ~ Women Sz 7 ~ GOOD , Converse Star Player Ox Navy White Unisex Leather Low-top Sneakers Trainers , CONVERSE All Star Light Hi Metal Grey 2015 RARE Sneakers Shoes Women Sz US 10NIKE WOMENS HAKATA RUNNING SHOES #AJ888-003 (BOX NO LID) , Skechers Women's Go Walk 4-14918 Walking Shoe - Choose SZ/ColorRyka Womens Jamboree Gray Mesh Fashion Sneakers Shoes 8.5 Wide (C,D,W) (1200) , Keds Women's Kickstart Eyelet Stripe Sneaker - Choose SZ/ColorSkechers Women's Grand Jams Replenish
"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."