Along the border where Martian plains turn from highlands to lowlands is a region where broad mesas and many locations evoke the Southwestern United States except for a key difference (besides being on another planet): there is evidence of glacier-like water ice.

This scene is of a tongue of material in Protonilus Mensae as it separates from a high-standing area that shows evidence of layering. The marbling present here and at the top of the curving extension of material suggest a possible icy origin, as many other Martian mountain glaciers show similar smaller lines and grooves.

The history of water ice on Mars, both at the poles and these more equatorial locations, is critical for understanding how Mars’ climate and water ice distribution may have changed from billions of years ago (when surface channels were likely formed by flowing water) to today (where most of Mars’ surface water is trapped in glacier-and ice-sheet-like features).

Written by: Margaret Landis  (13 August 2025)