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.Minnetonka Tunderbird II - Brown US 6LUCKY BRAND WOMEN'S BLACK WEDGE SLIP ON SHOES - Size 6 , Trotters Women's Josie Mary Jane Flat, Dark Blue, 6 2W USSANUK DONNA BLANKET RASPBERRY LANAI SIDEWALK SURFER SHOES, US 9/ ~NWT , Tory Burch Women's Jelly Bow Dark Orange Ballet Flat Shoes Size 7 M , Comfortiva Womens - Grace, Silver, Size 7.5 ZzHE , POINTER BOOTS CHAUSSURES PLATES DERBIES CUIR BLEU MARINE 38 LEATHER SHOES WOMEN , Crocs Isabella Jelly W Ballerinas - Black - TPUWomen's Reebok Gray Suede Sneakers US 10 Sz Very Clean! Nice Shape , Dansko Oksana Women Shoes Grey Cheetah Hair Calf Size 40 US 9.5-10 Nice , Vionic Womens Anchor Leather Moccasins - Bronze Metallic US 5Calvin Klein Womens lavida pebble grain Closed Toe Mules, Black, Size 8.5 6RG5 , Ann Taylor Matilde Tweed Ballet Flat Blue 8.5 Brand New!Womens Saucony Cohesion 9 Gray Running Shoes Size 6.5M (Z675)Reebok Classic White/Blue Leather Athletic Shoes Women’s 9 Style 1-62120 , EUC New Balance WT510BB Women US 6.5B Gray Blue Trail Running ShoesNew Balance Womens WZANTSI3 Running, Cross Training Shoes 5 Medium (B,M) 6582NEW ASICS Gel-Contend Womens Size 10 Running Shoes White/Purple/Black; NIBWOMEN'S NIKE ZOOM CAGE 2 TENNIS SHOES SZ 9 40.5 B USED 705260 607 SNEAKERSWomen's NEW SKECHERS WOMENS SPORT ENERGY The Queen Of Quality Athletic ShoesWomen's Aldo Women's Beige Shoes 7 High Safety FlatsWomen's Womens loafer shoes Customers First Flats , Madden Girl Runner Retro Jogger Sneakers Black 6.5MWOMENS PUMA SUEDE CLASSIC GOLD in colors BLACK / GOLD SIZE 7 , Womens Nike Free RN Motion FK 2017 Size 9 (880846 004) No Box , COLE HAAN STUDIOGRAND GREY GRAY SHOES LEATHER SNEAKERS SZ 8B BASKET WEAVED $250 , VANS New Authentic Pig Suede Vault Lady size USA 7WOMENS NIKE FREE RN RUNNING SHOES-SNEAKERS- 880840-401- GYM BLUE/ GLACIER BLUE , Skechers BOBS from Women's Bobs Squad-Double Dare Fashion Sneaker, Olive, 6.5...Demonia Women's Click 02-1 Mary Jane
"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."