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 WOMENS SPERRY TOP-SIDER BOAT SHOES A/O BLACK PATENT LEATHER SIZE 8.5 MEDIUM! , Soft Style Women's Veda Monk Strap Flat, Dark Grey Lizard, 9 EW USCole Haan Brown Leather Moc Toe Block Heel Loafers Flats Shoes Womens 8 B , AK ANNE KLEIN Patent Leather 'Faithi' Buckle Trim Loafer Shoes~Black~Size 6 MMEPHISTO MOBILS Derby Cuir Noir et Marron T 4.5 EUR/ T 7 US TBEBanana Republic 9.5 Blak Gold Ballet Flats Crackle EUC Career CasualWomen's Clarks Artisan brown leather wedge loafers slip ons sz 6M Too Cute!ENZO ANGIOLINI OMANIE Black Fabric Designer Flats Comfort 9.5 MLacoste Women's Marthe CRM Flat Slip On Shoes, Light Blue, Size 6 M US. , Women's Rockport Shoe Bets Seaworthy Pink Flats Size 7 M NEWECCO Womens sneaker, (Biom Fjuel Racer Cross-Trainer) size 8-8.5 ()Women's Merrell Barrado Brown Suede Leather Zipper Loafers US 6US WOMEN CASUAL JUTTI FLAT MOJARI BEADED SANDALS ETHNIC SHOES KHUSSA JOTI SS166 , BNWOT ASICS GEL Enduro 6 T0F7N Shoes White/Silver/Blue Sz 7 , Adidas Originals ZX Flux NPS Womens Girls Classic Casual Retro Trainers PinkRockport truWALKzero III Welded T-Toe Sneaker 6M , Keen Women's Voyageur Gray Leather Hiking Sneaker Womens Shoes 1004270 sz 9 MADIDAS CRAZYMOVE STUDIO Training Red Yoga Dance Ballet Shoes Womens 6 - 10Blondo Womens B3446 Black Leather Fashion Sneaker Size 9.5 (11013)Keds Sport Serenity Satin & Leather Slip on Sneakers Size 7m Cream/Peach color , Women's Ellie Women's Easy White On Sale Athletic ShoesEasy Spirit Tunein Slip On Mule Sneakers, BlackK-Swiss Women's Classic VN Iconic Fashion Sneaker - Choose SZ/Color , Fila C905S White Black Womens Lifestyle Casual Shoes Strap SneakersNew Balance Women's 247v1 Sneaker - Choose SZ/Color , New Balance Women's 690v2 Trail Running Shoes Blue Size 5.0Converse Chuck Taylor All Star Madison Ox Women's Shoes Blue/Silver 559907F , New Vionic Cypress Mid Brown Leather Trail Hiking-Walking Shoe 10 M/ MSRP $120 , $75 Women Keds Kick Purple Ditzy Floral Printed Canvas Sneakers Size 6.5mWomens Urban Outfitters Slip On Sneakers Size 6.5
"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."