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.Dolce vita women's ballet flats Shoes~ Black/white , Women's PROPET Black Loafer-Walking Shoe-Shootie With Side Zipper Size 8 , Rampage Women's Balley Almond Closed Toe Ballet with Bow and Memory Foam InsoleFranco Sarto Womens 9M Black Embossed Faux Leather FlatsMe Too Simone Clogs Slip On Shoes Mule Brown Suede High Heel Platform 10 M , SAS Tripad Comfort Womens Loafers 5.5 Bronze Metallic Leather Slip On Shoes USAMerrell Leather Loafer Slip On Quest Moc Brown Womens 6.5 , Nina Womens Quay2 Leather Pointed Toe Oxfords, Black Snake, Size 7.0Dansko Womens Size 10.5 Chocolate Brown Perforated Leather Mary Jane ClogsKork Ease Margaret Black Suede Perforated Shoes Sz 7.5 $130Sixtyseven Women’s Black Leather Oxfords Sz 8 Shoes 38 Snake Embossed , Skechers 49372 Womens Gemma-Space Trip Mule- Choose SZ/Color.Womens Buckle Punk Ballet Dolly Pumps Ladies Block Heels Ankle Strap Shoe LoaferBCBGeneretion Women's Pink Casey Sneakers Rare Colour , Size 10 USA , Calvin Klein Womens Inca 2 White Mesh Fashion Sneakers 10 Medium (B,M) BHFO 2028 , Women's nike Kaishi 2.0 sneakers 6NU.S. Polo Assn. size 5.5 shoes (inside shoe stained a little) , DANSKO WOMENS BLACK LEATHER SLIP ON COMFORT/PROFESSIONAL CLOGS SZ 7.5Fila Memory Pilota Women's Slip-On Memory Foam Grey/White/Mint Size 8.5 , cute womens bowknot slip on loafers platform round toe casual shoes wedge heelsClarks Everlay Dairyn Slip-On Wedge Loafers 290, Dark Tan, 7.5 US / 38 EUSalomon X-Ultra Women's Size 7.5 Hiking Shoes Contagrip Soles - Nice - Fast ShipCircus by Sam Edelman Women's Shania SneakerNew Dr Comfort Flex-OA Amy Diabetic Knee Pain Athletic Shoes Womens SZ 7M TaupeNew Balance Zante Running Shoes Gray/Pink Women's US 8.5 (A3,12) , Skechers Sport Womens Jackpot Fashion Sneaker- Pick SZ/Color. , Skechers On the Go City 2 Hibernate Chocolate Suede Womens Boots , Nike 472483-201 Air Rlty Royalty Highness VT Fashion Sneakers Women's US 7.5 , Skechers Women 23644 Navy Side By Side Comfort Shoes , **Skechers YOU - Movement Slip On Sneaker - Women's Size 8.5 - Black
"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."