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.Punjabi Handmade Traditional Embroidered Women's Ethnic Style Mojari Flat SliponRebecca Minkoff Women's Canvas Fashion Sneaker Size 6 , THOM MCAN SHOES WOMENS SIZE 9 M , Women's Franco Sarto SALLIE Blue Leather Perforated Slip On Flats Size 9 CareerB.O.C Womens suree Closed Toe Mules Black Size 6.5 t2aYNew Orthofeet Women Wichita Tan Washable Shoes Sz 6.5 4E XXW NO INSOLESDark Brown Leather KEEN Slingback Ankle Strap Low Shoes w/Floral Cut Out 7.5Womens Black Patent Vinyl Flats with Tassels Kelsi Dagger Mercy Size 9.5 NIB , MERRELL Woman's Mary Jane Shoes Black and Gray Suede Mesh Sz 7.5TOD'S women shoes sz 6 Europe 36 brown suede S6902NEW! CIRCUS by Sam Edelman Rose Gold Leather Flatform Buckle Shoes..9 M / 40 EUR , SALOMON WOMEN'S SZ 6 M 37.5 LIGHT GREEN SUEDE SLIP-ON LOAFERS HIKING SHOESBaskets dorées avec brillants Mosquitos en très bon état, taille 40 , Sperry Topsider Bluefish 2 Eye Boat Shoes, Bone, Leather, Womens 7 , New Santoni Italy Honey Tan Calf Skin, Penny Loafer / Driving 6.5 B , Rockport M77932 Coralee Plain Toe Canvas Sneakers, Women's Size 6M, RedAsics Gel Flux Women's Running Shoes Glacier/White/Hot Coral t3d9n- size 10Ryka Skylar Ladies Mesh Running Shoes size 9.5Saucony Womens ISO Series PWR Grid + Running Shoes Sz US 11 , NIB GUESS Genio High Top Ankle Sneakers Black Gold zipper US 6, , Dr. Scholl's Women's Hesper Slip-Resistant Mary Ja - Choose SZ/colorPUMA Women's Fierce Evoknit Metallic Wn Sneaker - Choose SZ/ColorNike Free 5.0 TR Fit 5 PRT Light Retro/Volt-Artisan Teal-White 704695-402 SZ 6.5 , Vans Gilbert Crockett Pro Navy/Tan Comfort Casual MEN'S 6.5 WOMEN'S 8 , 90s Woman's TOMMY HILFIGER Canvas Platform Sneakers/Shoes Size-5 1/2MNike Womens Sb Zoom Stefan Black Golf Shoes Size 11 (359622)Nike Womens MD Runner MID Hi Top Trainers Sneakers Shoes Black Multiple Sizes , Women's New Balance 1100 Size 6.5 D (6 1/2 wide) Walking Shoes - Brand NewADIDAS ORIGINALS TUBULAR SHADOW WOMEN'S RUNNING SHOES LIFESTYLE SNEAKERS , Reebok Work 'N Cushion KC Black Womens Work Shoes Slip&Oil Resistant V46976
"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."