The possibility that life took hold on early Mars got a boost this week with the announcement of the discovery of a previously "missing" mineral on the red planet.
New images from NASA's Mars Reconnaissance Orbiter show areas fo Mars where magnesium carbonate is exposed in 3.6-billion-year-old bedrock in Mars's Nili Fossae region.
Carbonate minerals contain carbon and oxygen and need liquid water to form. Common carbonates on Earth include limestone and chalk.
Previous missions had seen small percentages of carbonates in Martian dust. More recently the Mars Phoenix Lander found the minerals in the planet's arctic soils.
But until now, evidence for the source of these carbonates in Martian bedrock had been elusive, supporting theories that even if Mars once had bodies of water, they were too acidic to support life as we know it.
"Carbonate, like the baking soda in your refrigerator, dissolves quickly when exposed to acid," said study leader and Brown University professor Bethany Ehlmann yesterday at an American Geophysical Union meeting in San Francisco.
"So the fact that … carbonate is still present means that the waters flowing through [Nili Fossae] must not have been acid" and could therefore have been conducive to life.
Signs of CO2
Scientists had long expected to find carbonates on Mars, because the planet's carbon dioxide (CO2) atmosphere likely would have supported their formation.
Mars currently has a thin atmosphere, leaving the planet dry and frigid. But some experts think that billions of years ago the atmosphere was thicker, capturing enough heat from the sun to support liquid water on the surface.
Carbon dioxide gas should have reacted with Mars's volcanic rock, and that reaction should have produce carbonate, said Richard Zurek, a project scientist for the Mars orbiter based at NASA's Jet Propulsion Laboratory in Pasadena, California.
The newfound carbonate bedrock deposits are relatively small—some just under four square miles (ten square kilometers)—but large enough to hint at early Mars water sources.
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