A Geologic Map of Vesta Produced Using a Hybrid Method for Incorporating Spectroscopic and Morphologic Data

Abstract

We have constructed a global geologic map of the minor planet Vesta at 1:300,000-scale using Dawn spacecraft imaging, spectroscopic, topographic, and elemental data. In this effort, we used a mapping method that requires creating two maps independently: the first map uses morphology and topography to define map units, while the second map relies on multispectral data (“color”) to define units. The two are then combined into a hybrid product that retains the maximum amount of unique information from both maps in a readable format. This effort has revealed that for bodies where cratering is the dominant unit-forming process, and where there is not a close correlation between morphological feature types and multispectral signal, a hybrid mapping method better retains unique information carried by multispectral data during the mapping process than traditional morphology-based methods alone. Conversely, relying too heavily on color data risks placing too much emphasis on information drawn from the top few microns of the surface. To ensure both consistency and retention of unique information, we created a decision tree for determining which data would be primary in choosing where to draw unit boundaries. Also due to the significant amount of information borne by spectral data, we repurposed traditional mapping nomenclature so that subscripts carry color information. We recommend using this mapping methodology on bodies where (a) morphologic feature boundaries are commonly subtle, gradational, or both, and (b) spectral data carries a significant amount of unique data for identifying, characterizing, and interpreting geologic units.

A Geostratigraphic Map of the Rachmaninoff Basin Area: Integrating Morphostratigraphic and Spectral Units on Mercury

“…Yingst et al. (2023) did not quantitatively define their SUs of Vesta as Zambon et al. (2022) did for H05 on Mercury.…”

“…Yingst et al. (2023) defined a decision tree for determining whether geomorphological or spectral data should be used to define the position of a geological unit boundary where these data disagree and the position is ambiguous. In our map, as described earlier, where morphostratigraphic and spectral contacts closely coincide, we always retain the morphostratigraphic contact because these have been created using higher spatial resolution data sets than the spectral contacts.…”

“…Our method is similar to that of Yingst et al. (2023), who also made morphostratigraphic and spectral maps of Vesta before merging them. Our methods were derived independently and have some important differences.…”

“…Our method is applicable to regions of planetary surfaces where pre-existing morphostratigraphic and spectral maps are already available. In the future, when confronted with a planetary mapping area that warrants the fusion of morphostratigraphic and SUs, a mapper could choose to follow our method, that of Yingst et al (2023), or another method. Mappers should always follow the method that will best serve their science goals.…”

“…To address this problem for Vesta, Yingst et al. (2023) made two maps: the first, a conventional geomorphological map and the second, a spectral unit (SU) map. Yingst et al.…”