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.Tommy Hilfiger FRANK8 Flat Slip-On Mules 224, Black Multi Suede, 9.5 US , Women's Shoes Bamboo Jump 99A Almond Toe Ballerina Flat Chestnut *New*LOAFERS OXFORD KIDS SIZE 2 SLIP ON MY BUDDIES CLASSIC ASH RED CANVAS FLATS NEW , Tods Silver & White Leather Espadrilles Sz 36 Espadrille Flats , Daniel Green Velvet Flats Womens Size 8 Black Gold Horsebit Loafers -5238 , BORN BØRN Adeline Blue Leather Flat Loafers w/Pleated Toe - Size 7 US/38 EU EUC! , Corso Como Women's Black Leather Suede Flats 6 MCircus by Sam Edelman SZ 6.5 Leni Fries Before Guys Espadrilles Flats Shoes New , EUC J.CREW LOTTIE TASSEL FLATS IN SUEDE SIZE 9,5M BLACK , Franco Sarto Black Leather ELEGANCE--size 9.5B , **Bare Traps Kiah Metallic Slip On Shoes, Women's Size 10M, PewterSperry Topsider Womens Shoes NEW $90 Angelfish Oat Ivory Gold 5 M , CALIGARIUS / ITALY / EXQUISITE BALLET PUMP IN PEWTER PYTHON / 8 AA / EXCELLENTPropet Olivia Walking Shoe- Women's Size 8.5, TaupeNew Vogue Womens Furry Fur Round Toe Pumps Flats Loafers Warm Casual Boats ShoesDansko Animal Print Clogs Mules 38 Womens Wood Sole Shoes Slides Slip On LeopardSkechers Women's Kiss-Cheeky Loafer Black 8.5 M US , NEW$99 Women's Clarks Liz Ventura PREMIUM LEATHER COMFORT SANDAL , Adidas Womens Cloudfoam Ilation Mid Black/Black/Onix Basketball Shoes Size 9 , Attractive White Pink Beige LUCKY BRAND Fashion Sneakers Sz 8.5 , NIKE WOMEN'S INITIATOR WIDE SHOES SIZE 7.5 (WIDE) silver blue white 395663 001Womens Size 11 Asics Gel-hyper Tri Running Training SHOES T581N , Women's Women's Casual Slip-on Eco Shoes Reliable Quality FlatsNEW ASICS GEL COURT BELLA Women E655Y-8720 Paradise Green Pink Glow Shoe SZ 7.5 , NEW COLE HAAN WOMENS WOMEN'S GRANDPR? DECK MULE - PETAL NUBUCKAmazing Miniature American Shepherd-Women's Running Shoes-Free ShippingVANS SK8-HI SUEDE CANVAS IMPERIAL BLUE WOMEN'S SKATE SHOES /S89138.194New Women's Skechers 59837H Memory Foam Sneakers - Multi-Colored Size 8 (F20)Skechers Women's Bobs B-Loved Fame Time Dark Denim 31398/DKDN Memory Foam NewNike FS Lite 2 Running shoes Light Blue white Coral Ladies 11 worn once 684667 ,
"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."