That's a Relief

A color coded shaded relief map of a symmetrical mountain located in Mare Ingenii and centered at 35.969°S, 164.497°E. This peak is approximately 2.5 km in diameter and 230 meters tall. The colors represent elevation; high elevations are red, and low elevations are blue [NASA/GSFC/Arizona State University].

Within Mare Ingenii, there are multiple striking landforms. Perhaps the most studied are the swirls that decorate the mare in beautiful patterns. Nearby one of the swirls is the symmetrical mountain (opening image). Is this mountain a volcanic feature (perhaps a dome, shield, or cone) or a remnant of preexisting terrain that was embayed by a flood of basalt (kipuka)?

LROC WAC image of Mare Ingenii. The blue arrow indicates the mound of interest. This image is approximately 120 km wide [NASA/GSFC/Arizona State University].

The circular feature is more reflective than the mare that surrounds it. In this case, the Sun is coming from the west, illuminating the western slope, so perhaps the eye is simply seeing the effect of topography facing the Sun? Or could the higher reflectance also be the result of a composition difference? If the mare and the circular feature were of the same composition, we would expect to see a smooth gradient both in the reflectance and the topography as you move from the mare up onto the mountain. In this case, however, the boundary between the mare and the mountain is sharp.

An orthographic view of LROC NAC image M121131127 centered at 35.969°S, 164.497°E. The mountain is approximately 2.5 km across [NASA/GSFC/Arizona State University].

If only the NAC image is used to interpret this landscape, this mountain might be classified as a dome (a volcanic landform). However, the color coded shaded relief and the color coded slope map (below) suggest that this feature may be a highland kipuka because it has slopes that are too steep to indicate a low shield and because it lacks a summit crater or fracture like one might expect of a volcanic dome, shield, or cone. Kipukas are the remnants of preexisting terrain that have been embayed by mare basalt but remain partially exposed at the surface. These could be crater rims, peaks, or large ejecta blocks. These features are often hard to distinguish due to gradual wearing down and rounding of the slopes. Though the flanks of the mountain are smooth, it is low in iron and titanium, which is consistent with highlands material. To unambiguously classify this mountain, fieldwork and sample analysis are necessary. 

A color coded slope map generated from an LROC NAC DTM and centered at 35.969°S, 164.497°E. The colors represent slope; blues are more flat (1-3°), and orange is steeper (~11°). The mountain is approximately 2.5 km in diameter [NASA/GSFC/Arizona State University].

Explore the full NAC DTM below!

Related posts:

Lunar Swirls at Mare Ingenii 

Depths of Mare Ingenii 

Wrinkled Reiner Gamma

Published by H. Meyer on 1 October 2013