Some of the layered material is light-toned. Rocks containing sulfates have a light tone compared to isolated rocks examined by landers and rovers at other locations on Mars. Rocks in Meridiani have strong evidence for past water, including the mineral jarosite.
Also visible in a Context Camera image, our high resolution picture shows layers exposed where the crater ejecta has been eroded.
Image: NASA/JPL/University of Arizona https://www.uahirise.org/hipod/ESP_064524_1835