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.Easy Street Women's Giver Flat, Black, Size 6.0Womens Shoes Black Patent Flats Teagan Beacon Sofwear 9.5M NIB AM , Sociology Women's Pointed-Toe Flats With Cutouts Cognac Brown Size 6.5AK ANNE KLEIN Comfy Shiny Beige Flexible Leather Slip On Flat Loafers 7.5M EUCBorn Concept Brown Suede Leather Women's Loafers Size US 8.5 Eur 40 Buckle Strap , Women shoes spring and Autumn pointed deep soft bottom casual student strap flatWomen's Size 7.5 Pink Sequin Sperry Top Sider Boat ShoesEastland Womens Yarmouth Camp Moc Slip-on- Pick SZ/Color.MERRELL Shoes Brio Comfort Casual Mary Janes Flats Womens Dark Brown Sz 9.5Boden Womens Jackie Heels Sz 39.5 9 Metallic Silver Leather Heels CareerWomen's Skechers, Go Walk 4, 14900, Majestic Walking Shoe, Black/WhiteWomens Sperry Top Sider Angelfish Boat Shoes Size US 10 M Purple White PlaidNIB Cole Haan Rosalie Cap Toe Ballet Flat, Black Patent Leather, Size 6.5Vince Camuto Halette Brown Womens Shoes Size 8 M Flats MSRP $98STUART WEITZMAN BLACK TASSEL LOAFERS SIZE 6B , Cat & Jack Boys Black High Top Tennis Shoes Size 13 Running Walking Sports , Fila Women's Spherical Silver/Monument/Aurora Sneaker 8M , Easy Street Womens giddy ll Closed Toe Slide Flats, White, Size 6.0 1FwE , Women High Top Rivet Platform Shoes Platform Wedge Heel Ankle Booties Hot B_sea , Clarks Collections Women's Sneakers Size 8M Black PinkUnder Armour Marbella Tropic Running Women's Shoes Size 10 , SPERRY TOP- SIDER SZ 8.5 M BLACK PATENT TRIM BLACK & WHITE ZEBRA BOAT SHOEAdidas Alphabounce 1 Running Shoe - WomensEd Hardy Original women's high sneakers, new with tags HR702W size 6,7,8,9Nike Wmns Lunarepic Flyknit Shield Water-Repellent Black Silver Women 849665-001 , NWB Adidas Mana Bounce Black/Vista Grey/Super Blush US Women's Size 7 B-Medium , Nike Air Max Thea Athletic Shoes - Women's Size 7.5, TaupeReebok Instapump Fury Sand Gary White Pink Blu US Size 7 FREE SHIPPING BRAND NEW , NEW SKECHERS SKECH AIR 2.0 WOMENS MEMORY FOAM SHOES , Puma Blaze Of Glory X Size? X Bodega Women's Sz 6 23cm Ronnie fieg ,
"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."