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 women’s fashion platform shoe us size 7/37(Asian ) blackSperry Topsider Womens Orange Gold Leather Firefish Boat Loafers Shoes - SZ 8 M , Preppy Style Mori Girl Japanese Cosplay Students Black Leather Shoes Lolita #ILWomen's Size 8 Cole Haan Brown Leather Strapped Casual Loafers , Dr. Martens 6 Brown Platform Shoes Women'sSperry Top-Sider Pier View Elastic Gray Canvas Boat Shoes Women's Size 7 M , Womens shoes size 9. Color: Black Made by:Earthe Origins by EarthKlogs NATALIE Clogs Women's Black Oiled Leather Display Model 14 W , VAN ELI - WOMENS METALLIC BRONZE BUTTON EMBELLISHED LEATHER BALLET FLATS-7M-NEW! , NIB Naturalizer "MUSIC" Black Leather Slip-on Shoes sz 7 NBar III New Involve Brown Womens Shoes Size 7.5 M Flats MSRP $79.99BOBS from Skechers 34338 Womens Bliss 2.0-Restart Ankle BootieWomens J-41 shoes - size 7.5 - Horizon black , Chic Womens Pointed Toe Rivets Decor Loafers Flat Shoes Pumps Skull Party New , Naya Debbie Women's Penny Loafers Brown/Beige casual Shoes Size 7 W , 2017 Cow Muscle Ballet Summer Flower Print Women Genuine Leather Shoes Woman FlTOPSHOP 'Kylie' Backless Silver Metallic Leather Mules (6.5M US) NWT $85 , Hurley Womens Sneakers Casual Size 7 BrownEasy Spirit Quickset Slip-On Mule e360 Size 11 M Black , Vintage 90s Reebok New Womens 8 Transition Court Canvas Casual Tennis ShoesVans Sk8 Hi Mid V (2 Tone) Black/Racing Red Kids 12 , WOMENS HOKA ONE ONE CHALLENGER ATR 3 RUNNING SHOES 8.5 1014762Men's Shoes Slippers Glerups Boot Slipper Brown 46.0 Attractive And Durable SlippersWomen's Norse Kubo Orthotic Friendly shoes Terrific Value Flats , women's shoes D.A.T.E. ( date ) 7 () sneakers blue silver textile BX59-38Women's Nike Air Zoom Strong 2 921335 005 Training Crossfit Multiple SizesMBT Shoes Women's Chapa GTX Gray Gore-Tex Rocker Walking Size 7.5RARE VINTAGE 2005 Adidas Samoa Womens Athletic Shoes Size 8 White Blue Gray , Women's size 6 Converse All stars Purple multi colorsNew Vans Old Skool Zip Leather Zephyr Mint Green Blue/Blanc Skate Shoe Women 5
"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."