Penitentes

This image depicts the Chajnantor Plateau — home of the Atacama Large Millimeter/submillimeter Array (ALMA) — with an icy forest of penitentes (Spanish for “penitents”) clustered in mid view. The penitentes are a curious natural phenomenon found in high-altitude regions. They are thin spikes of hardened snow or ice, with sharp edges pointing towards the Sun, reaching heights from a few centimetres up to several metres. You can read more about penitentes in this Picture of the Week (potw1221).