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.SPERRY Women's Bahama Rose Cordovan Sequins Boat Shoes Faux FUR Lined, Size 7 M , Sporto Winter White Sweater Knit Ballet Flats & Earmuff Set LG 9-10.5 NEW , A New Day Women's Huntress Knotted Silver Metallic Slide SandalsWoman Pointed Flats Faux Leather Cut Out (dia05) , NATURALIZER WOMEN’S SHOES Navy Blue Size 9.5M**Crocs Lina Ballet Flats, Women's Size 7, Black , B Makowsky Grey Leather Double Ring & Bow Tie Loafer 5 NewMinnetonka Womens Brown Suede Mules w/Shearling 8Etienne Aigner Black Ally Leather Loafers Flats Shoes w Tassles - 8M - USED , ORTHOFEET Womens Size 6D Bone Tan Napa Leather Strap "Acadia" Diabetic ShoeSAS Viva Tripad Comfort Brown Leather Slip on Mocs Loafer USA Women's 7.5 NNEW***THEORY Sz 9M leather fabric HI TOP WEDGE brown animal print!!Womens CLARKS Artisan Leather Slip-On Comfort Heel Loafer Shoes Brown Sz 8 MVANS OFF THE WALL WOMENS CANVAS SHOES FLATS SKATEBOARDING SHOE GRAY/BLACK 6.5M , NEW! Skechers Women's FLEX APPEAL 2.0 SIMPLISTIC Shoes Blk WIDE W 166A azSaucony Grid Excursion TR5 Running Shoes Women’s Size 6 US Excellent PlusWomen Size 9.5 Nike Dart 9 White Purple Trail Running Shoes 443863 A0109PEARL IZUMI JB WOMENS Silver ATHLETIC RUNNING WALKING TENNIS SHOES SIZE 9New Bella Vita Womens Emilie Black Fashion Shoes Size 6 , Adidas Honey MID Women's Sneakers 919460 NewADIDAS HONEY MID WOMEN'S CANVAS SNEA , Womens Nike Air Max 2014 Pink White Green Volt Size 10 (621078-600) RunningNIKE WOMEN'S CLASSIC CORTEZ STR BLAVK LEATHER Black TRAINET 884922 001 SIZE: 8Women's Adidas Alphabounce HPS AMS - Talc/White/Talc - Width: med - RunningSkechers Skyline Grey/Lavender Womens Sporty Shoes Size 6.5MCole Haan Womens Garlandsam Low Top Slip On Fashion Citrus Red Size 6.0Skechers Performance Women's Go Run 600 Refine BKW Black/White MediumNew Balance WTE412S1 All Terrain Trail Running Shoes Sneakers Women's Sz 11 , Adidas Supernova Glide Boost 7 Womens Running Shoes Sneakers B33605 Sz 8 M , Women’s Asics GEL FIT NOVA Athletics Shoes, Purple, Size 9.5, Eur 41.5Rocket Dog Junglegym Women's Causal Pumps Plimsols Fashion Trainers Pink ,
"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."