The new study points to ferrihydrite as the culprit for Mars’ color. This is basically water-rich iron. So, the researchers think the planet was first covered in water for a decent amount of ...

Many dyes change color with an increase or decrease of pH making it possible to ... is most available in soil with a pH range centered around 6.5. Extremely and strongly acid soils (pH 4.0-5.0) can ...