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.CLARKS "STRUCTURE" LEATHER MARY JANES....SIZE: 8.5.........EXCELLENT CONDITIONBrinley Co. Women's Scrunch Flexible Stretchy Side Round Toe Ballet Flats 9New Grosby Women's Comfort Floral Embossed Warm Slipper Victoria Cheap , gloria-33 New Fashion Nubuck Slip On Casual Women Flats Women Shoes Black 7DUCK HEAD WOMEN'S BEIGE LETHER FLAT LOAFER SLIP-ON SHOES SIZE 8 MEDIUMChatties Size9-10 Large Ladies Fashionable Flats Shoes Sandals-White-SHIP N 24HR , Aerosoles Women Brown Cork White Patent Cap Toe Low Heel Ballet Flats Shoe 10 , NEW SANUK KITTY HAWK WOMENS BEIGH SIDEWALK SURFER SLIP ON SHOES US 10 EUR041COLE HAAN Women's Size 7.5 ZeroGrand OS Slip-On Shoes Sneaker Grey Black D44030Taupe MERRELL PLAZA BANDEAU DARK TAUPE WOMEN'S MARY JANE SHOES 8.5 Suede LeatherKork-Ease Nessa Black Leather Women's Flat 7.5MGUESS Marciano Women's Size 7.5 Platform Loafers Black Leather Slip On Wedges , Klogs Women's Clogs Display Model Shoes Astra Black Square 10 M , Sally O'Hara Women's Slip-Ons Ballerinas Real Leather, Black Soft Inner SoleSkechers BOBS From Women's Pureflex 2-Inlite FlatEasy Street Women's Kacey Flat, Brown Flannel/Snake, 7.5 W USKelly & Katie Womens dotty Closed Toe MulesWomens Asics Rocket Running Cross Training shoes size 8 B257N , Propet Womens Black/Pink Running Shoes Size 8.5 (20420)Brooks Transcend Running Shoes Blue Synthetic Women8Medium (B, M)Rocket Dog Jazzin Bubble Stripe or Jungle Palm Sneakers Size 6 , Women's NikeFlex 2017 Running Sneaker 7.5 Fine Workmanship Athletic ShoesWomen's Franco Sarto Womens Stacey High Quality And Inexpensive Flats , Reebok Size 6 Pink Running Sneakers New Womens Shoes , New Sperry STS82434 Oasis Canal Black Women's Boat Shoes 6 USNike Free TR 7 Reflect Women's Training Shoes White/Blue Mult Sizes AA2238 , Nike Air Huarache Run Ultra Women's Sandals Solar Red Sea Coral Size 8 NEW , Funtasma Women's Exotica 2000Womens Skechers Sport Women's No Limits Slip-On Mule Sneaker 22752 BKWP #BR , Asics Gel-Kayano 22 Womens Blue Pink Athletic Sneakers Running Shoes Size 9
"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."