Geology of the Eminescu (H-09) quadrangle: Mapping status

Abstract

The coordinated Mercury’s global mapping project (Galluzzi et al. (2021), aims at delivering quadrangle geological maps for the entire surface of Mercury by using the available basemaps derived from the NASA MESSENGER Mercury Dual Imaging Systems (MDIS) images. The NASA MESSENGER mission was able to cover the surface of Mercury with an average resolution of 200 m/px globally. This allows to produce a series of 1:3M regional geologic maps to be used in support to the ESA/JAXA BepiColombo mission. Here we present the status of the geologic mapping of the Eminescu (H-09) quadrangle, which covers the area between latitudes 22.5°N, -22.5°S and longitudes 72°E, 144°E. The selection of this quadrangle was based on its wealth of many interesting features (e.g., Beagle Rupes, hollow deposits on Eminescu crater, pyroclastic deposits at the margin of the Caloris basin) and on the color variability between the different terrain types that allows to reconstruct the geological history of H-09.

Methods

In this work, we used the available basemaps derived from the MESSENGER MDIS instrument images, such as the monochrome morphology image mosaics at high- and low-incidence angle (BDR, HIE, HIW and LOI) with a resolution of 166 m/px, together with the enhanced-color and 3-color global mosaics, having a resolution of 665 m/px.

The chosen 1:3M output scale is achieved by mapping at an average scale of 1:400k, which is appropriate for the used basemaps. For the symbology, we applied, and in some cases revisited, the Federal Geographic Data Committee (FGDC) and the United Stated Geographic System (USGS) recommendations. The classification of the crater types was based on their diameter, degradation degree and superposition order. The crater's ejecta, central peak, and floor morphology (hummocky or smooth) were distinguished and mapped only for craters larger than 20 km, to avoid the saturation of map features. The terrain units were identified by means of morphology and crater-density, by distinguishing between smooth, intermediate and intercrater plains. We used different symbologies for geological contacts and linear features by distinguishing between certain and approximate contacts, or certain and uncertain/hidden structures, respectively. In particular, the linear features layer encompasses morphologies such as crater rims (up to 5 km in diameter), fault scarps, wrinkle ridges and volcanic vents. The variability in color and albedo was digitized within a surface features polygon layer (e.g., dark material, bright material, and hollow clusters). We did not consider details smaller than 4 km, nor linear features whose distance was smaller than this same threshold to avoid map readability issues.

Results

The mapping of H-09 is still in progress. The preliminary analysis shows an intriguing morphology related to endogenic and exogenic processes, where intensive tectonic and cratering structures constitute together the main geological events that provided the heterogeneity of terrains in the quadrangle. The tectonic events were probably driven by global cooling, however, we found both compressive and tensional tectonic features on the surface. Hollow clusters are spread all over the quadrangle in different sizes and locations (e.g., crater floors, central peaks). The Eminescu crater located in H-09, between latitudes 12.3°N, 8.8°N  and longitudes 115.9°E, 112.2°E in H-09, is a relatively young crater on Mercury's surface and is characterized by extensive ejecta for one radius from the crater's rim and a recently hollowed central peak. These features and its enhanced color variability will probably require a higher-resolution study of this crater by integrating the geomorphological map with spectral data.

This map will be the first geological product for this region with such a scale. Once the mapping is completed, we will be able to determine the absolute ages of the units to classify the terrains in chronological order and provide a complete geological and morphological analysis to understand the geological evolution of the quadrangle. Therefore, through the mapping of H-09 we aim at supporting the ESA/JAXA BepiColombo mission to Mercury by targeting all interesting features and contributing to the investigation and the understanding of Mercury.

Keywords: Mercury (planet), Eminescu Quadrangle, Geological Mapping, MESSENGER, MDIS.

Acknowledgements

This research has been supported by European Union’s Horizon 2020 under grant agreement N° 776276-PLANMAP.

References

Galluzzi et al. (2021), PGM Meeting 2021, LPI Contrib. No. 2610.