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.Aerosoles Women's Nubuck Alteration Moc Slip On Casual Blue Gray 10.5 11M $89 , Sperry Top-Sider Women's A/O 2-Eye Boat Shoes Brwn Sahara 9155240 Sz 5.5 24774 , Women's Casual Leather Comfort Walking Flat Shoes Moccasin Slide Size US 8Merrell Primo Patch Black Leather Walking Shoes Womens Size 6.5 MDREW Last Women Brown Z Strap Suede Mary Jane Shoe Size 8.5WW , WANTED SHOES WOMEN'S MIDNITE BALLET FLAT GOLD SYNTHETIC US SIZE 7.5 MEDIUM (B)MSANUK KATS MEOW Grey Gray TEXTILE SLIP ON Flats Sneakers WOMEN'S SHOES SIZE 7SAS Free Time Women's Size 7.5 Oxfords Casual Black Leather Shoes (Inv Y)G.H. Bass Co. Womens Dark Brown Snake Textured Shoes 7 MSoftspots Women's Leather Comfort Shoes Sz 7M , Spring Step Hearts Womens White Mary Janes Cross Strap Shoes Size 41W(US:9.5-10New Franco Sarto Women's 'Malina' Flat Leather Black Shoes Sz 6.5 , sperry's womems boat shoes sz 5 laguna maroonNew Jeffrey Campbell Play Zomg Leopard Print Trainers size - US 6 () ()Canvas Casual Athletic Tennis Shoes Womens No Boundaries 11 M Off White , Nike Shox White Silver Womens Running Shoes 331152-115 US 8Merrell Circuit MJ Brown Sport Mary Janes Ortholite Shoes - Womens Size 7 , Sperry Seacoast Casual Shoe- Women's Size 8 M, WhiteKeds Women's Tan Zipper NWOT Flat Sneakers USA 10//(#Lot2 , PureSole Heather Grey Deven Slip on Sporty Shoe 9 NEW , Women's ASICS Gel Rocket 6 Volleyball Shoes Size 8 USWomen's Bamboo SHOES WOMENS SIZE 8 Excellent Quality Flats , PUMA Glyde Lo F Green WhiteSize AU 7 / / Women's Gold Class Shiny Fashion Sneakers / Trainers , DS 2009 NIKE TERMINATOR HIGH PERF PRM QS DAY & NIGHT supreme wms 9.5 men 8 tz , Women's Nike Air Max Correlate Trainers Sneakers Purple/Silver SizeAsics Gel Cumulus 12 White Blue Silver Running Shoes Cross Train Women's 9.5 EUC , AHNU WOMEN YOGA SPLIT BLACK SHOE US 8.5 / / NIBPuma Drift Cat 5 Shoes Black Rhinestones Women Sneakers 305197-01G , Rockport Womens Sz 8 M Gray Textile Light Weight Athletic Running Shoes NICE!! ,
"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."