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.Euc CLARKS STRUCTURED COMFORT SLIP ON/CASUAL BLACK LEATHER SUEDE PATENT 8M MINTNicole "Garrett" Womens Sz 8M Taupe Ballet Flats w/ Sparkle Bow EUCBallet Flats Kids Ballerinas CCC Ladies Wet Look Dolly Shoes Patent Pumps SizeNICE Women's Cole Haan Country Slip-on Slides Shoes Loafers Brown Leather-7 AACirca Joan & David Black Leather Driving Shoes Horse Bit Womens 9 1/2MBrighton Women's Colby Two-Tone Leather Loafers Black/Brown, Made in Italy, US 6ARAVON Size 8.5 M Brown Leather Low-Heeled Slip-Ons Dressy Casual Loafers , Franco Sarto brown leather round toe buckle slip on loafer block heel 9WNEW Skechers Women's Pureflex Fashion Slip-On Flat - Size 7.5Airwalk Women's Shoes Sz Us Us 10.5 Eur 41 Black & White Synthetic Slip On , Vaneli Women's 'Scarlet' Black Suede Flats Size 6 M , ST JOHN'S BAY CAREER FLATS LEATHER BURGUNDY ANIMAL SNAKE PRINT 11W FREE SHIPPING , NEW Free People Rajah Beaded Flats Silver/Black Leather Size 36BORN Red Brown Leather Suede Loafers Shoes Women's 8 39 , Clarks Artisan Blue Leather Flats Shoes Loafers Woman's 8Chinese Laundry Synthetic 'Burdine" Glitter Star Loafer Flat in Gold Size: 8Footprints by Birkenstock Oxford Casual Brown Leather Women US 8 Narrow , KEEN Sienna Casual Shoes, Brown, Leather, Women's US Size 6 , Talbots Brown Reptile Textured Loafers Slip On Shoes Women's Size 6.5 USDANSKO WOMEN'S PROFESSIONAL SLIP-ON CLOG BLACK CABRIO 36 6 MEDIUM $140 , Rj's Fuzzies Slipper Sheepskin Mens Soft Sole Moccasin Shoe Medium (D, M) 11 , Men's Shoes Slippers Glerups Boot Slipper Green 43.0 Wholesale Slippers , Skechers Synergy 2.0 Simply Chic Trainers Womens Memory Foam Slip On ShoesCONVERSE BLANK CANVAS CTAS 70 HI TOP SPOTTED JACQ SIZE WOMEN 8 MEN 6 , Vans Authentic Gore (Studs) Skyway Blue- Women's Slipadidas FortaRun EL K Strap Black Silver Kids Junior Youth Running Shoes BY8995 , New Nike Dart 11 Women Running Shoes Sz. 10 - 724477-100Merrell Siren Sport Womens 6.5 M Trail Hiking Shoes Leather Brown Orange vibram , Nike 749177 Womens Flex Experience RN 4 Casual Running Shoes Sneakers , Scott eRide Support 2 - Red - Womens ,
"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."