Mars - Curiosity Sol 1185 - What is this?

This image was taken by MAST_RIGHT onboard NASA's Mars rover Curiosity on Sol 1185 (2015-12-06T19:39:00.000Z). NASA Image: https://mars.nasa.gov/msl-raw-images/msss/01185/mcam/1185MR0053760000602491E01_DXXX.jpg Audio: Som ET - 65 - Mars Credit: NASA/JPL-Caltech/MSSS