Geologic layering on Mars. image from the HiRISE high-resolution camera on board the Mars Reconnaissance Orbiter (MRO) shows multiple layers of exposed sedimentary rock on Mars in a region known as Arabia Terra. Referred to as cyclic bedding” by geologists, this pattern of layering is caused by repeated fluctuations in the amount of sediment available to create new rock layers. This is often caused by long-term changes in the climate of a region, or even by wobbles in a planet’s rotation which can make certain areas experience long periods of dry climate followed by periods of wetter climate.