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.Comfort-Well by Beacon shoes womens size 7.5M brown 1.5" heel comfort careerLadies Black Glitter T-Bar Jelly Shoes with Cut Out Detail F80046 , NEW WOMEN'S COMFORTVIEW SLINGBACK PUMP (SHOES) BLACK IN COLOR SIZE: 7 1/2 MWomens Summer Beach Wedding Outdoor Flat Ballet Crystal Glitter Jelly ShoesClarks Artisan Brown Soft Leather Slip On Mule Clogs Shoes womens 9 Woven BuckleEASTLAND Women's Shoes Size 7.5M Leather Career formal Slip On BrownSKECHERS Women’s Slip On Memory Foam Flex Sole Gray/ Green Shoes Sneakers 11Converse One Star Women's Gold Leather Fashion Platform Sneaker Shoes Size 8.5Ladies Shoes Cherry Lynch Zip up Black or Red Casual Comfort Shoes Size 6-10 NewA2 by Aerosoles Trend Right Flat - Women's Size 6.5 M, Black , AMALFI Rangoni Siry Oxford Suede Burnt Yellow Vintage Shoes Florence Italy 3.5Easy Spirit New Kristy Beige Womens Shoes Size 6.5 M Flats MSRP $79Splendid Jaime Brown Womens Shoes Size 6.5 M Flats MSRP $98Asics ~ Attack Women's XC Shoes ~ Model GN254 ~ Size 10 , Kedsport Casual Sneakers,#WF20640M, Dark Taupe, Womens US Size 7.5 , Kodiak Candy Steel Toe Composite Plate Oxford Women's Black Shoes 7MDiscounts 2017 Fashion Genuine Leather Casual Loafers Shoes Women Sandals SummerSupremes 7.5 Wide Taupe Sneakers Women's ShoesSuperga New Linembrw Blue Womens Shoes Size 10 M Flats MSRP $159 , Easy Street Kila Slip On Sport Flats, Black Shimmer, 5 US , Skechers You Luxe - Grey - Womens , Reebok Zig Tech Women US 5 Silver, Pink + Blue Athletic Running Shoes ZigtechDVS Equinox Women’s Size 9 US Black Ecru Suede BMX DC Skate Shoes SneakersNew Balance 574 [KV574FYY] Sneakers Kids Gray Blue White ? US 5 ? Free Shipping , Asics T757N GT-2000 5 Running Training Athletic Shoes Sneakers Blue Womens 11Nike Free RN 2017 Lightweight Running Shoes, Women's Size 8.5, Black , Adidas Kanada TR5 Blue Pink Synthetic Mesh Running Trail Shoes Women's 7.5M , Danskin Now Women's White Athletics Shoes Size 8.5Brooks Womens Adrenaline GTS 13 Running Walking Shoes Size 10B Silver Gray/Blue , NEW Reebok CrossFit Speed TR womens running shoe BD2565 trainers white 41 10 US ,
"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."