Post contributed by Dr Colman Gallagher, UCD School of Geography and UCD Earth Institute, University College Dublin, Ireland.

Viscous flow features occur in the mid-latitudes of Mars and have characteristics consistent with being debris-covered glaciers. Climate models suggest that martian glaciers are cold-based systems in which meltwater has never been widely produced but Gallagher et al. (2021) described a widespread assemblage of landforms in Phlegra Montes (Image 1) that are morphologically analogous to landforms classified by Glasser and Bennett (2004) as indicative of warm-based glacial erosion on Earth. This suggests that glaciers in this region produced meltwater in the past. Warm-based glaciers reach the melting point at their beds, allowing them to slide over their beds and erode the underlying landscape. Meltwater produced by warm-based glaciers can also flow across the bed and erode subglacial meltwater valleys. Landforms of glacial erosion identified by Gallagher et al. (2021) include zones of aerial scour, glacial troughs (Image 2), corries (cirques; Image 3), lee-side rock cavities, streamlined bedrock forms, rock grooves (Image 4), subglacial meltwater channels (Image 4), and tunnel valleys. This is in addition to a depositional glacial meltwater landform called an esker, which was discovered by Gallagher and Balme (2015) and you can read about in a previous post here.

Image 1. Elevation map of Mars showing the location of Phlegra Montes. Blue regions are low elevation and red/white regions are high elevation (MOLA elevation data credit: USGS, NASA, JPL).