New evidence of carbonate-bearing rocks on Mars' surface suggests that at least some of the planet's ancient water was not as acidic as previously thought.
Using a spectrometer on the Mars Reconnaissance Orbiter, a team of U.S. scientists detected some carbonate minerals in a region of valleys called the Nili Fossae.
These minerals are probably in volcanic rocks that have been weathered by water whose pH is relatively neutral, according to their study published in the latest issue of journal Science.
This handout image, released Nov. 20, 2008, shows a perspective view of a mountain in the eastern Hellas region of Mars surrounded by a lobate deposit with flow textures on the surface. New evidence of carbonate-bearing rocks on Mars' surface suggests that at least some of the planet's ancient water was not as acidic as previously thought. (Xinhua/Reuters Photo)
Although Mars has had the raw ingredients for forming carbonates -- water, basalt and an atmosphere with carbon dioxide -- scientists have been unable to find large areas of carbonates on Mars before now.
One of the leading explanations for this mystery has been that acidic waters either dissolved the carbonates or prevented them from forming. In particular, Mars' middle epoch, the Hesperian, has been proposed as a time when acidic weathering was common.
The new carbonates, which occur in small exposures of rocks (less than 10 square kilometers), are accompanied by clay minerals, further suggesting that local waters were neutral or even alkaline at the time these minerals formed.
The authors suggest that ancient Mars hosted a variety of wet environments, whose waters' acidity varied widely. "Such diversity bodes well for the prospect of past habitable environments on Mars," they conclude. Source:Xinhua