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.ZIBU "Sannie" Chestnut Brown Slip Ons Clogs Loafers Walking Shoes - Size 9M EUC! , Womens Oka.B Black/Blue Jelly Ballet Flats - Sz 10Michael Antonio Perri Womens Size 10 Pink Textile Ballet Flats Shoes "Casual Women Athletic Shoes Thick Platform Hollow Running Walking Comfy SneakersMushroom women's slip on leatherquilted black loafers shoes size 9WDANSKO Dk Brown Leather Clogs Sz 38REPORT Women’s Size 8 1/2 M Brown Suede Moc-Toe Ballet FlatsClark's Artisan Leather Loafers Slip On Women's Size 8.5MSporto Jenna Brown Leather Jenna Mary Jane Flats 8 SALEGiani Bernini Zohar Comfort Flats Size 10 Metallic Leather & Mesh Slip On TaupeDansko Black Leather Strap Mary Jane Slip On Clog Shoes Womens US 8.5-9SANUK MOLLIE DUSTY BLACK SIDEWALK SLIP ON SHOE US 9 / / NWTWomen's Skechers, 34270, BOBS with Memory Foam World Slip on Flats, Black , HISPANITAS Ballerines Elastiquées Cuir Bleu Pétrole Talons Compensés T 40 TBEForever 21 Tennis Shoes High Tops Leather Sz 8 , New Women's Skechers e'Lites Fresh Start Sneakers - Black Size 6 , New Balance WX623v3-Womens Size 9D-White-Pre OwnedAkademiks Red White And Gray Womens Sneakers Size 8.5 New!! , Vans UltraRange Rapidweld Athletic Shoes - Women's Size 6, White , ECCO White Gray Stripe Casual Sport Athletic Walking Shoe Women / US 8 8.5Women's NIKE LADIES SHOES 40 Ample Supply And Prompt Delivery Athletic ShoesNIKE Hyperdiamond 2 Keystone 856434-018 WOLF GREY Size 6.5Nike Air Max 90 mesh GS premium reflective silver sparkle black womens 6.5 5Y , Adidas Edge Lux 2, Size 9 , VANS Sk8 Hi (MTE) Parisian Night/Blanc Suede Outdoor Boots WOMEN'S Size 7Bronx Women's Kay Kay , Reebok 2 Quick Electrify Running Women's Shoes , NEW Women's New Balance 620 v2 Trail RUNNING Shoes WT620LB2 Size 5 B , Brooks Ghost 6 Running Shoes Women Size 8 Great ConditionNEW adidas Women's Tubular Defiant Sneaker Shoe OFF WHITE / GREY Size 8.5 M
"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."