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.Black White Striped Basic Ballet Flats Shoes Knot on top NWT Women's Size 11Avanti Beige/Orange/Brown Canvas Espadrilles FLATS Slip On Size 6 GENTLY WORN! , XOXO LADIES METALLIC TEXTILE FLATS-9M-LEATHER INNERSOLE-BARELY WORN-ELASTIC-CUTE , SAM EDELMAN GRAY METALLIC SHOES sz 37 US 6.5 MNine West Succeed Loafers Size 6.5M Gold Leather Slip On Shoes WomensVia Spiga Black Patent Leather Elastic Casual Loafer Women's size 9LPB Ballerine Ella Metal C Argent , New Scholl Orthaheel Valiant Womens Comfort Casual Supportive Shoes , CLARKS 01707 ASHLAND BLUSH WOMEN'S BLACK LEATHER SLIP ON SHOES NEW IN BOXSame Edelman Cassie Mules, Women's Size 9.5 M, PinkEverlast Sport Women' Sneaker Memory Foam ~ Light blue ~ Sz 7 79911 , Pieces Paris Women's Monochrome Suedette Slip On Thick Platform Sole Loafers New , The North Face Women's 6.5 Cradle Running Shoes Snake Plate , Women Rhinestone Flat Heels Square Toe Slip On Oxfords Formal Shoes Zsell , New Vans Womemns Authentic Lo Pro TC Canvas Athletic Shoes US 7 , NEW BALANCE "WE060" Casual SHOES WOMEN SIZE US 7 med EURO 37.5 NEW , Women's Asics Gel-Contend 3 Shoes Sneakers Size 10 Running Purple Mint Pink M15 , TEVA Ochoa Sport Slip On Shoes WOMENS Size US 7 Green WATER BEACH SN 6301 , New Balance Womens w560ls7 running course Fabric Low Top Grey/Teal Size 5.5Women's Used Vibram toe shoes-women's Genuine Athletic Shoes , Women's JANA Escarpin 22404 Noir For Your Selection FlatsWomen's crocs size 6 flats Year-end Bargain Sale FlatsSkechers Breathe Easy - Brisk Fleet Black Blk Womens Casual Comfort Size 7.5MReebok Fury Adapt Triple Black Women Running Casual Shoes Sneakers BD2408Puma duplex evo futur minimal safety yellow glacier gray free shipping , Vans Authentic Kendra Dandy I Scream White Sz Womens 6.5 NIBSkechers Women's GO Walk Satisfy Gray Walking Shoes - Size 9/9.5 NWB 14149 , NIKE Zoom Rival M8 Track Field Sprint Running Spike Shoes. Size 7.5Creative Recreation Size 7.5 M Cesario White Fashion Sneakers New Womens ShoesSam Edelman Collins Watermelon Sneakers Women Size 9.5
"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."