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.Women's No Brand Ballet Flats Soft Hot Pink Size 9 1/2 Casual Shoes NEWWomen's LAUREN BY RALPH LAUREN SLIDE ON FLATS Brown Leather Size 8 AlligatorBass Womens Size 10 M Brown Leather Mary-Jane Flats Shoes , �MINT� WOMEN'S SAS TRIPAD COMFORT SHOE PENNY LOAFER METALLIC GRAY LEATHER 8 MMunro Women's Jerrie Narrow Black Suede Slip-On Size US 7N , FABULICIOUS Round Toe Ballet Flat Glitter Fabric Rhinestone Shoes TREAT-06 Nude , Women's Anyi Lu Bordeaux Leather Ballet Flats Black Patent Toe Caps 37 EU / 7 US , Women's Sperry Top-Sider Intrepid Navy Boat Shoe Size 5.5 , Jessica Simpson Womens praylee2 Closed Toe Classic Pumps Champagne Size 9.0 yXKlogs Sondra Women's Clogs Display Model Shoes Black Smooth 11 M , Klogs Missy Womens Leather Clogs Display Model Shoes Zentangle 9.5 M , Women's Shoes Hinge RN58665 CA57963 Silver & Black Leather Slip On Flats Size 7MSteve Madden Women's Santi Dress Sandal Size 9 M US , Nike Lunarglide iD + Running Shoes, Black/Wht/Gry, Womens US Size 9Ladies Puma shoes size 8.5 excellent condition Soft Foam , Womens Running Sneakers Casual Athletic Breathable Walk Sports Shoes Trainers SZ , Ladies Women Flat Slip On Plimsolls Zip Glitter Skater Pumps Trainers Shoes Size , New Life Stride Womans Flats Size 6 Ricki Beige Espadrilles Bow SlingbacksLifeStride Womens diverse Closed Toe Loafers, Taupe, Size 9.5 8gxyNike Air Women’s Shoes Sneakers Trail Hike Athletic Gray Yellow Size 7 ShoesWomens Fashion Cute Glitter Leisure Sequins Loafers Cartoon Flats Sneaker Shoes , WOMENS NIKE AIR MAX Correlate Leather Gray 525381-001 SIZE 8.5 USAthletic Shoes , ON SALE! The North Face Womens trail shoes Alkaline gtx Gore-Tex Size 6.5 10Brooks Ghost 7 Size US 10 Women's Running Shoes Blue 1201611B451 Sneakers , Canvas Shoes Print Cat Top Sneakers Athletic Womens shoes Cute , New* Woman Nike Lab Free RN Motion FlyKnit FK 2017 Size 9.5 Blue Grey 880846-402 , Nike Wmns Free TR 6 Cross Training Womens Shoes Grey Blue 833413-007 Size 9.5Vintage 1993 Womens Nike Sneakers White Blue Pink Size 9.5, Retro 90’s! , NEW Nike Women's FS Lite Run 3 Premium Size 6.5 Bright Blue 844670 400 , NIKE WMNS AIR MAX THEA PRINT Lt Blue Lacquer/White-Clear Water -599408 401-
"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."