| Duricrust | |
| Mineral: | Soluble minerals |
| Climate: | Arid |
| Composition: | Various |
| Composition Secondary: | Various |
Duricrust is a hard layer on or near the surface of soil. Duricrusts can range in thickness from a few millimeters or centimeters to several meters.
It is a general term (not to be confused with duripan) for a zone of chemical precipitation and hardening formed at or near the surface of sedimentary bodies through pedogenic or non-pedogenic processes. It is typically formed by the accumulation of soluble minerals deposited by mineral-bearing waters that move upward, downward, or laterally by capillary action, commonly assisted in arid settings by evaporation.[1] [2] There are different types of duricrusts, each distinguished by a dominant mineralogy. For example, ferricrete (laterite) is dominated by sesquioxides of iron; alcrete (bauxite) is dominated by sesquioxides of aluminum; silcrete by silica; calcrete (caliche) by calcium carbonate, and gypcrete (gypcrust) by gypsum.[1]
Duricrust is often studied during missions to Mars because it may help prove the planet once had more water. Duricrust was found on Mars at the Viking 2 landing site, and a similar structure, nicknamed "Snow Queen", was found under the Phoenix landing site.[3] Phoenix's duricrust was later confirmed to be water-based.[4]