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.Rainsport shoes, black, zip front, sz. 8M , Jutti Indian Leather Flip-Flops Women Shoes Khussa Ballet Flat Mojari US 6.5 , DANA BUCHMAN Womens Darcy Red Slip On Flats 1.5" Heel Bow Silver Accents Sz 9 MKEDS ELEANOR WOMENS CANVAS PANDA PRINT SLIP ON SNEAKERS SHOES SIZE 6 M , PERRY ELLIS AMERICA All Star Ballet Flats Yellow Vtg Polka Dot Sz 8AA , Walking Cradles Womens Shoe Black 9.5 , SAS Tripad Comfort EASIER Womens Leather Loafers Flats Wedge Sz 7M Pewter SilverNew Women's Stylish Almond Toe Buckle Zipper Low Heel Booties Shoes Size 5 - 11 , Women's Michelle D Gray Striped Bow Toe Ballerina Ballet Flats Size 9 MARIAT Distressed Metallic Bronze Leather Slip On Western Clogs Shoes Women's 8 BKeds Womens Coursa Metallic Black Sneaker- Size 6.5/7/7.5/9.5 NWB WF57864Darlene Women by Soft Style Flats Black US 10N , ARRAY Womens Freedom Leather Square Toe Loafers White Size 9.0 j5cnStuart Weitzman Brown Patent Leather Mules Slides 8 AA , Savannah F0878 Ladies Slip On Mule Pewter Synthetic (34A) (Kett) , LANVIN Embellished Ballerina Flats (SIZE 9.5) , Klogs Sondra Women's Clogs Display Model Shoes Black Smooth 7 WIsaac Mizrahi Saddle Brown Suede Pointed Toe Loafer Flats NEW Maggie , Alfani Womens Aleaa Almond Toe Ballet Flats Apricot Size 7.0 9ZXQ , Bobs From Skechers Women's Plush Lite - Sox Shop Gray/White Casual Shoe 7 WomenQupid Women's Moira-07 Sneaker, Champagne, Size 7.0 aVFqNIKE Flex Experience RN2 Women's Running Jogging Shoes Grey Teal Aqua Blue Sz 8New New Balance Womens Wl696noa Blue Walking, Hiking, Trail Shoes Size 11 , Women's Xa Pro 3D GTX W Trail RunnerWomens Reebok Crossfit Nano 5.0 Kevlar Cross Training Shoes. Size 7.5 Nice!!!Women's Puma Women's Sneakers 6 US Fine Workmanship Athletic Shoes , New Balance Women's Size 9.5 W560LG6 Gray Blue Athletic Running Shoes ZV-1480 , Nike Flex 2016 RN (GS) Girls Youth 834281 006 Sz 4-7 Fast Shipping K S , Nike WMNS Kaishi 2.0 II women lifestyle casual sneakers NEW wolf grey pink blast , Skechers Women's GOwalk Slip-on Sneakers Purple 7
"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."