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.New Josef Seibel Beige Leather Flower Mary Janes Flats Women's 39 / 8-8.5 , Merrell - Women's size 6 1/2 Casual Slip-On Shoes , Brand New Women's Fashion Ballerina Ballet Flats Size 5 - 10BCBG White Bling Flip Flops - Wedge Heel - Women's 10 , MEPHISTO Woman's US 8 UK/5.5 Brown Croc Patent Leather Loafers Cool AirTalbots women tan leather upper rubber sole pattern loafers shoes size 5.5MBORN BLACK LEATHER MULES WOMEN SZ 7 MCovington- Brown Leather Slip On Square Toe Loafers- Size 11 , Sperry Top-Sider Women's Beachwalker Black/Lime Water Shoe 6M , Brooks Transcend 2 Womens Teal Running Shoes Size 8 WORN tennis Athletic Blue , Natural Comfort Pia Womens Leather Comfortable Mary Jane Flat ShoesClarks shoes Women’s size 9M White Leather Athletic Walking , Rocket Dog Shoes Loafers Walking Running Hiking 6 Brown Beige Blue Athleticadidas Women's Barricade Team 2 Tennis ShoeMuffins Platform Sport Fashion Sneakers Casual Wedge High Heel Women Shoes Sbox1new 2018 handmade mens slippers mens sandals leather slippers shoe sandals flatSkechers Women's SkechAir Cross-Trainer Shoes Size 7.5 Black & Hot Pink , Brooks Launch orange and navy athletic shoes - womens 7.5, euro 38.5 , Rocket Dog Women Navy Plaid Sneaker Shoe US 8M Pre Owned , Asics GT-2000 Womens Running Shoes - Gray/Pink/Blue - Sz 7.5Ahnu Women's Size 6.5 Sugarpine WP Blue Star Athletic Hiking Trail Shoes ZV-1276 , BROOKS Womens Ravenna 8 Blue Running Training Athletic Shoes Size 7.5 IP-21 , Women's WOMENS~Vintage~LEATHER CRAFT~Brown~LEATHER~Huarache~SHOES~Flats~OPEN TOE~Size 11 Elegant And Sturdy Package FlatsWmns Nike Air Max Thea Ultra FK Flyknit Multi-Color Rainbow Women 881175-600 , Nike Womens Blazer Low SP pedro White Chrome 718802 100 Size 11.5 = Mens Size 10New Balance womens shoes W990KM3 Koman sneakers pink 990 Made in the U.S.A. WIDE , New Balance Women's Zante v3 Running Shoe Ozone Blue WZANTBB3 B Width , Women's Onitsuka Tiger X Asics -Ultimate 81 (HN567 4801) - Hawaiian Ocean/WhiteMizuno paradox 2, womens 9.0 WNike Womens Zoom Strike Running Shoes Size 5 (36383)
"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."