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.SAS TRIPAD COMFORT FOOT BED SHOES WOMEN'S SIZE 6 1/2 WLIDDY-3-07 WOMEN PLATFORM OXFORDS ELEGANT BRONZEWhite Casual Patent slip on Ballerinas Trendy Shiny Dolly Girls Ladies sz 7.5Clarks Bendables Womens Brown Leather Mule Shoe - Size 9.5M , Nine West Womens Anastagia Pointed Toe Ankle Strap Mary Jane Flats , St. Johns Bay Gray Suede Wedge Loafer Shoes Size 8.5 M Buckle Leather TrimSBICCA Casual Briwn Women’s Shoes Sz 7W , Splendid New Womens Ranger Navy Floral Linen Boat Shoes 8.5 M ShoesTalbots Women's Flats Size 9 Lavender Slingbacks Leather Soles DressySKECHERS BOBS BLACK FIDDLERS SLIP-ONS FLATS 6.5Oliberte Blanca Suede Flats - Women's Size 10, NavySAS TRIPAD COMFORT BLACK SUEDE WALKING SNEAKERS WOMEN'S 10MNWT $119 Klogs Leather Naples Black Nurse Medical Clogs Shoes 7 MNIKE AIR MAX TRAINING FUSION WOMEN ATHLETIC RUNNING GYM SHOES SNEAKERS SZ 9Women's New Balance 461 Sz 6B Sneakers Shoes Trail Running Fitness Pink Gray M09Merrell Salida Trekker Hiking Shoe Women Sz 8.5 Brown Leather with Purple , CONVERSE LADIES CHUCK TAYLOR HI CHILLI PEPPER RED 139841F , CROCS Jibbitz Kilby Women's Smoke Slip On Clog Mules Shoes Size 9 NEWWomens Saucony Grid Stratos 5 Silver Trainers Size 7.5M (V781) , NEW Qupid Paisley-01 Rose Gold Embossed Studded Sneaker , Women's Mizuno Wave Enigma Gray/Purple/Green Running Shoes US 8Merrell All Out Blaze Sieve Shoe - Women's Size 9 M, Brown Sugar/BlueNEW UNDER ARMOUR THRILL 3 RUNNING SHOE 1295770 SELECT GRAY-PINK OR GRAY-BLUE $70Skechers Sport Women's Black Good Stuff Fashion Sneaker Size 9.5ASICS Womens Gel-Venture 5-W Silver Grey/Turquoise/Lime Running Shoes Size 11 DNIKE Women's Air Max Ivo Running Shoes Thunder Blue Orange 580519 400 Size 7.5 , Adidas Originals MIDIRU court 2.0 mid shoes G61142 Womens size 8 US! RAREMustang Ladies 1252-302-259 GRAPHIT Lo Sneakers TrainersSkechers Play On Womens Sneakers Black Size 9.5MSaucony Guide 7 Running Shoes Silver/Royal Blue Men's US 8 Eur 41 (L4,6)
"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."