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.Womens 9.5M ETIENNE AIGNER White Pebbled Leather Driving Flat Moccasin Shoes , Teva "Shay" mush SUEDE mary jane split toe casual shoe sz 7 M OLIVE brown greenGEOX RESPIRA - ESPRESSO SUEDE FLATS w/BOWS - LADIES 37.5/7.5EUC Banana Republic Flats Ballerinas Mocasins Tan Leather Beige Size 7 , Sofft Women's Black Leather Mules Clogs Heels Shoes - US 9 M , Lucky Brand Aaron womens Driving Mocs Leather Faux Fur lined shoes size 8 B , Vtg sz 37 Eur 7 US Handmade Tooled Leather Shoe Tan Slide Mules Slipper NOSNew Lauren Ralph Lauren GAEL Leather Loafer Flat Wedge Moc Shoe Blue/Off-White 6Dansko 40 US 10 Women’s Metallic Silver Mary Jane Slip On Comfort ShoesBCBG Maxazria Womens Shoes Size 6.5 36.5 Black Leather Open Toe Ballet Flats , POINTER BOOTS CHAUSSURES PLATES DERBIES CUIR BLEU MARINE 38 LEATHER SHOES WOMEN , Taryn Rose Womens Beverly Closed Toe Mary Jane Flats, Pewter, Size 5.5 IciI , WOLKY Womens Style 1950 38 US 7 Suede Leather Walking Shoes Rubber SolesEasy Spirit Womens GANNET Almond Toe Espadrille Flats, Red/Multi, Size 9.5 , New Balance 744 All Terrain Women's Size 7 - Barely worn - Full Tread Fast ShipWomens Under Armour Rapid Le , STY / BES / BLK , Size; 10.5Womens Slip On Patform Canvas Hidden Wedge Heels Sneakers Sport Shoes Creeper , Womens Round Toe Sneakers Hidden Wedge Heel Platform Vogue new hot Slip On ShoesTommy Hilfiger Frank3 Slip-On Fashion Sneaker 498, White, 8.5 USConverse CTAS 70 Hi Woven 151244C Shoes Black Size 6 NewAvia Journey - Brown - Womens , Women's QUPID Jewel Embellished Buckle Strap Low Top Sneaker - White , Nike Womens Size 8.5 Free TR FlyKnit Sneakers 718785-0 Training Bright CrimsonPuma Suede Colored Simply Green 36058401 Leather Classic Casual WomenOn Cloud Womens Cloudrunner Gray Running Shoes Size 6.5 (410606)Skechers Women's Seager - Stat Scalloped Collar, Engineered Skech-Knit Slip-onSkechers Women's Performance GoVulc 2 Glint Slip On Black 14593/BBKVANS Sk8 Hi Slim (Light Gum) Raspberry Rose Pink Skate Shoes WOMEN'S 6.5 , Skechers Flex Appeal 2.0 Insights Womens Sneakers 8- Select SZ/Color. , Skechers Shape Ups Mary Jane Sparkle Double Strap Toning Rocker Shoes SZ 7.5 EUC
"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."