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.DR SCHOLL'S RED WOVEN LOAFERS FLATS DOUBLE AIR PILLOW INSOLE NWOB 8 M FREE SHIP!Clarks Collection Women's Size 8 M Brown Slip On Slides Leather Casual Work Shoe , NEW..'Enzo Angiolini' CREAM Reptile-Print Foldable FLATS...8.5 Travel Perfect! , Unknown Brand Women's Multi-Color Textile Slip On Jute Loafers Sz /US 5.5 , Rockport XCS Slide Sandals Women's Size US 9 SlippersEUC BORN Concepts Womens Heeled Slip On Mule Clogs Size 7M Color BlackAerosoles Womens betunia Closed Toe Slide Flats Black Size 9.0 DVEg , SKECHERS Womens Grey Leather Mary Jane Flats Comfort Shoes Sport Size 9 , New Women's Skechers De Ja Vu Fashion Sneaker Slip On Shoes 22660 Taupe 36D , SAS Walk Easy Women's Diabetic Walking Shoes Black Nubuck Leather Sneaker US 9 MAGL Attilio Giusti Leombruni Ballet Shoes Black Suede Patent Toe Sz 9 US / 39 EUCole Haan Zerogrand OS Pink Seude Leather Wingtip Women’s Shoes Sz 9.5 , Klogs NATALIE Clogs Women's WHITE Smooth Leather Display Model 12 W**Anne Klein Onmyway Flats, Women's Size 9.5, Pewter , CLARKS Women's Dowling Pearl Walking Shoe, - Choose SZ/ColorAqua Zumba by Speedo Wraptastic Sandal Vivid Violet size 5 USReebok Women's Yourflex Trainette 8.0l MT Training Shoes, Purple/Black, 10B M905Converse Limited Edition Simpsons High Tops Men’s 7 & Women’s 9 , WOMEN’S SIZE 7.5 BLUE & WHITE PINSTRIPES KEDS CASUAL SHOES , ASICS Amplica Blue - Womens - Size 7 BDraven Canvas Duane Peters Shoes Rockabilly Goth Scene Emo Skate Punk Tattoo 8.5 , Adidas CrazyMove TR Womens Athletic Training Shoes NEW with box 9ROSHE ONE LAVA PINK YOUTH SIZE 6.0 SAME AS WOMAN 7.5 RUNNING NEWadidas Outdoor Women's Terrex Voyager CW CP W Walking-Shoes , Vionic with Orthaheel Technology Women's Noosa Flip Flop Sandal Silver , Asics GT-2000 4 Running Shoe - Women's Size 7 - Black , adidas Pure Boost X Element Running Shoes-Women's size 8.5 BlackMizuno Women's Wave Enigma 5 Athletic Running Shoes Silver/Blue Atoll , nike women kaishi 2.0 wvn cool grey running sz 11 shoes 917532 001 , Skechers 8 M Black Multi Synergy Air Streamer Slip On Sport Mule 11964/BMLT
"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."