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.Nwt Womens Old Navy Brown Fuzzy Leopard Slip On Loafers Flats Shoes 6NEW Zara Man Black Leather Military Heavy Track Boots Size US 6 / NWOB A28WOMEN'S CLARKS WAVE WALK BROWN LEATHER TOP STITCH BUTTON LOAFERS 9 N 86564 , Clarks Artisan Womens Brown Leather Fashion Sneakers Size 7 M , Women's Karen Scott Bayside Beige Loafers Shoes US Size 5 M , NEW FREE PEOPLE BLACK LEATHER PARADOX PEARL WRAP SLIDE LOAFERS SZ 7.5-8/38 $130Women's Stuart Weitzman Black Patent Leather Beaded Studded Flats Loafers 7AA , Zee Alexis Women's Sammi Woven Mary Jane Shoe Black Metallic 40 US 9.5 , Lucky Brand New Emmie Blue Womens Shoes Size 7 M Flats MSRP $69.95 , Easy Street Women's Jules Flat Blue/White 8.5 2E US , **SKECHERS - Instant Hit Sneaker, Women's Size 9, Black/Silver (REPAIR)Stuart Weitzman Women's Metallic Gray Leather Slip-on Flat Size 6.5MNew! Women's Skechers Conversations 22551 Charming Fashion Shoe - Black/Grey G43NIKE Women's Flex Supreme TR 4 Cross Trainer Black/Purple/Crimson Size 6.5 ftts , New! Women's Easy Spirit Traveltime Athletic Mules White SZ 10 23040114 D39New Balance 928v2 Women's RollBar Walking Athletic Shoes Size 9 BWomen's Deep Rhythm -Fitkicks Special Edition In Many Styles Athletic Shoes , Women's embroidered mules Comfortable Feel FlatsNew Puma 96 Hours Lancio Tessuto Women's Shoes Rare US6 , Skechers BOBS Women's Beach Bingo-Dog House Party SneakerSkechers Relaxed Fit Fortune-Knit Memory Foam Sneakers Shoes , ASICS Women's Gel-Encourage LE Tennis Shoe , VNT NEW Puma Nuala Women's 8 Tan Suede Trainer shoe outer snap 1990s Orig Box , *Brand New* Ryka Grafik Flow Training Shoes with Pivot Point in Grey/Blue Sz 9.5Womens Nike Footscape Metro TLO Black lawn Concord Vivid Blue 325215-031 , Nike ZOOM STRIKE Womens White Grey AJ0188-100 Athletic Training Shoes , Nike Air Max 180 Women's Running Shoes Size US 6.5 Red & White , adidas Originals Women's ZX Flux W Running Shoe, Grey, Size 11.0Steve Madden Women's Lynn Sneaker - Choose SZ/color , Converse Ctas Gemma Hi Egret/Black/ Womens Hi top 553448C, NEW, US size 7 ,
"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."