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 Ladies Flat Studded Sliders Slip On Summer Mules Casual Rock New Size , Dr Scholls Double Air Pillo Advanced Comfort Womens Leather 7.5 W Work ShoesWomen's Faded Glory Size 5.5 Brown Suede Mules , GU Dolce Vita 11M Nude/Blush/Cream Cealey Embossed Huarache LoaferLadies Havaianas Slim Logo Metallic Beach Holiday Flip Flop Sandal All Sizes , ARRAY Womens lizzy Leather Closed Toe Loafers, Black, Size 5.0 , Womens DR SCHOLL'S Sky Blue Leather Casual Slip-on Flats Loafer Shoe 6M - LNCClarks Cloud Steppers Slip-on Shoes - Sillian Black 9.5W , NIB ! P.W. MINOR XTRA DEPTH WOMENS ERIKA SHOES 79110 Size: 5.5 B Color: Clay , New Balance Suede Slip-ons US Size 8 , Easy Spirit Nidia flats black leather sz 9 Med NEW , Pin Up Couture Women's Cutiepie 08 , Cape Robbins Polo Fashion Patent Metallic Leather Platform Flatform Rose GoldNike Women Yellow Track Spike Zoom Rival - 615998-307 w/ tool & Spikes Size 10MBT Sz 9.5 KAYA Mary Jane Shoes Blue Beige Nubuck Leather Toning No Reserve , Women's Ryka Kailee - Black/Purple/Grey - Width: med - Fashion Sneakers , Saucony Grid Cohesion 10 Women Gray Blue Running Shoe S15354-2 Size US 9.5 , Zoot Sports Ultra Kane 2.0 - Blue;Silver - WomensSaucony Ride 8 Women's Sz 9.5 Narrow Running Shoes Silver Blue (WA1) , Womens Saucony Grid Stratos 5 Silver Trainers Size 7M (V68)Converse Chuck Taylor All Star Ox Womens Pink White Canvas Trainers , Nike W AF1 Upstep Premium Metallic Platinum 917590-001 Women's Shoes Size 7.5Womens Skechers Slip-Ons Deep Space Black/Multi Memory Foam Womens Size 5 1/2 , NFL Seattle Seahawks Canvas Sneakers Size 8 US Bradford Exchange NewXtratuf Women's Yellowtail Royal Blue/Grey Size 10 Slip On ShoesVANS New SK8-Hi Reissue 2-Tone Vault Lady size USA 7 , Nike Women's Equalon+ 4 - White/Utility Blue-Metallic Silver-Grey (375282-141) , Nike Air Max Thea Mid Black/Black-Metallic Pewter 859550-002 Women's SZ 10Nike New Blazer Mid Cut Black Womens Shoes Size 5 M Fashion Sneakers MSRP $100Women's Ryka Valerie - Blue/Red/White - Width: med - Slip Ons ,
"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."