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.424 Fifth Womens Gabby 1 Tan Embellished Loafers Flats 7 Medium (B,M) BHFO 2899 , Charter Club Joeey Round Toe Espadrilles 507, Blue Stripe, 6.5 US , SALE Ladies Spot on Fuchsia open toe flat shoe slip on F1929 , Merrell Women's Brown Slip On Sneaker Vented Moccasins Sz 8.5 Mules Comfort (b28Gaimo Women Espadrille Flats Size US 11 Beige GoldBorn Studded Loafer Women size 7.5 Black Leather�MINT� WOMEN'S ETIENNE AIGNER TAN LEATHER BLOCK HEEL LOAFER "RUSH" Sz 7.5MMERRELL Relay Tour Beige Mary Janes Mj Strappy Walking Shoes Women's Size 6 36Dansko Julie Loafer Brown Nubuck Leather Women Shoes Size 8.5 Walnut Suede , NAOT 37 US 6 Brown Leather mary janes Excellent comfort casual kirei , NEW BALANCE White Leather & Mesh Tennis Shoes Women's Size 8 B - WCT1002WWomens Gold Glitter sequins Kitten heels Slip on Court Party Boat Shoes Pumps , Women's MEL 228342 black jelly open toe flats w/ bows sz. 6 (37)NEW Fieramosca & Co ITALY black leather Flat Loafer Shoe Women Ladies 5.5 5 1/2WOMEN'S CLARKS 'BENDABLES' DARK BROWN CLOGS SIZE 8 M , Levis Womens Stan G Canvas Slip On Sneaker New Without Box , Mizuno Wave Inspire 9 Women's 11 WIDE Blue/Green Athletic Running Workout ShoesDC Women's 11 Athletic Shoes Plaid Tartan Brown Textile Embossed AlligatorWomens 7 M Vasque Talus Trek Low UltraDry Waterproof Hiking Shoes Green LeatherNike Flywire High Tops size 6 preown , WOMENS ATHLETIC SHOES NEW BALANCE BRAND SIZE 9.5 LEATHER UPPER WHITE ZR7Anne Klein Womens Guardless Fabric Low Top Slip On Fashion Navy Multi Size 6.0PUMA Aurora Borealis Pink Violet Gold Shimmer Hitop Gold Logo Sz 9 Unreal Color , New Balance Womens WW812 BE Walking Shoe Bone Size 7 B US , TEVA MAHOGANY ARROWOOD WP LEATHER SNEAKER TRAIL SHOES, WOMEN US 7/ ~ NIBHoliday Keds Christmas Green Red Black Metalic sz 8.5Asics Gel-Noosa TRI 8 (T356N) Running Women's Shoes Multi-Color Size 9.5 SH19$109.95 Women's Sz 7.5 Monument Merrell Siren Edge Waterproof Hiking ShoesJsport by Jambu Catskill Gray Fashion sneakers shoes Womens 7.5 M, EUC , Reef Girls Deckhand 2 Womens Fashion Sneaker- Choose SZ/Color. ,
"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."