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.Call It Spring Women's Coredda Black Flat 7M , Kelly & Katie Womens cigola Closed Toe Loafers, Light Pink, Size 6.5 DzWCST. JOHN'S BAY BLACK SHOES WOMENS SIZE 7 , H & M Women's Pale Pink Slip On Round Toe Ballet Flats US Size 7Lucky Brand Womens Emmie Blue Ballet Flats Shoes 6 Medium (B,M) BHFO 9217 , NEW Ladies Flats by Faded Glory, Size 7.5, Silver, NEW , **Sperry Seaside Leather Perf Loafers, Women's Size 5.5 M, Rose , Old Beijing Cloth Shoes Flax Facial Makeup Slippers Embroidered Shoes Sandals Co , Sperry Top Sider Womens Neon Zebra Print Sequence Boat Shoes Loafers Size 7Easy Spirit Womens dixiee Leather Closed Toe, Gold Leather, Size 8.5Soludos Women's Smoking Slipper Espadrille Wink Sand Size 8 239 , Skechers Sport D'Lites Women's Sneakers Athletic Running Walking Size 7 WOW!!! , Vision Street Wear Womens Canvas Hi Skate Shoes, Turquoise, US 8.5New Balance 560 v6 Blue/Gray/Silver Running Shoes (Womens US 10 B) W560LG6 , British Womens Girls Metal Buckle Decor Low Heels Casual Leather Round Toe Shoes , ARRAY Womens Closed Toe Loafers, Pewter, Size 8.0 e9jOSteve Madden Womens Noe, Pewter, Size 7.0 dzWB , Sperry Top-Sider Women's Seacoast Core White Fisherman Sneakers Size 9.5M (E87)NEW CHASE & CHLOE FLORAL EMBROIDERED PLATFORM SNEAKERS CELINE1 , Skechers Womens - Gray Running Shoes Size 9 (326430) , New Men's Classic PU House Slipper Durable Rubber Bottom Warm & Comfortable-270 , Asics Gel-Contend 4 Grey Green Women Running Shoes Size 9? T765N , Brooks Glycerin 10 Pink Black Silver Trail Running Shoe - Women's 7 Medium , Sketchers Women's Shoes Size 8.5 Shape-ups Leather Suede Mary Jane Strap BrownSaucony Freedom Iso Unisex Road-Running-Shoes - Choose SZ/ColorCustom Fashion And Comfortable Women Boots Super Mario Martin Boots For GirlReebok Fine Leather High Top Sneakers Pink Red Wm's sz 9, 40 Eu Vtg 1990 CrestsCreative Recreation Women's w Dano Sneaker, Maroon, Size 8.0ASICS Gel Nimbus 17 NYC New York City Marathon Shoes Womens Size 12.5 T5M8NNew Balance 610 v5 Women’s Purple/yellow All Terrain Shoes 8.5M
"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."