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.KEEN Womens Size 5 Sienna Gray Brown Canvas Slip on Mary Jane Walking Flats , Born Women Size 8M Brown Suede Leather 1 Eye Oxfords B68955 Size 8/39 M/WFERGALICIOUS ADELE WOMENS PLAID WHITE BLACK SLIP ON ADORABLE FLAT SHOES SIZE 7MCole Haan Air Pinch Penny Black Loafers Women’s Sz 6.5Women's Naturalizer Black Leather N5 Comfort Slip On Loafers 7 M , KLOGS CAMILA LEATHER CLOGS DISPLAY MODEL TEX MEX 7.5W , Ballerine MAM'ZELLE chaussure plate femme sneaker sport mocassin CUIR.36.NEUF , TROTTERS Women's LIZ Black Woven Leather Slip On Loafer Size US 6.5W (T5158-581) , Skechers Performance Women's Go Walk Gray Walking Shoes ~ Memory Foam 8.5 W , Women Elegant Bow Leather Flats Mules Shoes Oxfords Loafers Comfort Ankle BootsSperry Womens Brown Suede Plaid Moc Toe Boot Size 8.5 M , Stuart Weitzman Taupe Patent Leather Square Toe Flat Size 7.5M RH12088#DREAM PAIRS New Men's Suede Leather Sheepskin Fur Lining Slipper Loafers Boots , Asics Gel Scram 2 Sneaker - Women's Size 7 Black/Pink , Earth Origins By Earth Carly Nubuck Leather/Mesh Slip-On Shoes Women Size 12 NEW , NIB adidas ORIGINALS Tubular Defiant Women 6.5 WHITE nmd boost xr1 yeezy ultraSkechers Women's EZ Flex 3.0 - Wild N Free Casual Aqua 7.5 US M , Converse Chuck Taylor Shoreline Sneaker 558871C Size 5.5 , NEW Womens NIKE Air Visi Sleek 396042 103 White Hot Red Silver Sneakers ShoesConverse Chuck Taylor Low Top Velvet Pink Ladies Sneaker Size 8Skechers Performance Womens Go Fit-TR Walking ShoePurple8.5 M USSkechers 15100 Womens Go Run Fast Cross Training- Choose SZ/Color. , Adidas Womens - Gray Running Shoes Size 7.5 (362831) , VANS OLD SKOOL CHESTNUT BROWN WOMEN'S 8.5 SKATE SHOES/ S89105.183Drew Shoe Women's Fusion Comfort Sneaker Black Size 10 M EUCNIB Womens Size 7 Merrell 1SIX8 Moc AC+ Black Fashion Shoes Sneakers NewSKECHERS Women's og 98 GARDEN PARTY NAVY FASHION SNEAKERS DESIGN IN LA SZ 8New Adidas Women's F5 TRX GF Low Soccer White, Pink and PurpleWomen’s Reebok Crossfit Nano CF74 Shoes Size US 10 Green DuracageFessura x Free People Womens Edge Mask Sneakers Violet Size 41 New
"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."