THE MODERN APPROACH AND RATIONALE FOR PLANETARY GEOLOGIC MAPPING

Geological maps provide the contextual framework for understanding the formative histories of planets. These are based on consistently documentable characteristics of rock and sediment units as well as their spatial and temporal associations with one another. The geologic mapping concept – that a planetary surface can be uniquely differentiated into three-dimensional bodies of lithic material – is relatively straightforward. However, strategies and tactics differ depending on the body of interest, the scale of the map, and the background of the mapper. Mappers must be aware of and adhere to (1) community standards (including geodesy and nomenclature), (2) past mapping and topical science results, (3) cartographic design, and (4) scale-appropriate scientific representation. Mapper preferences result in variance between maps and repeatability within the bounds of such variance hinges upon clear and consistent documentation and representation. Modern geologic maps are constructed using not only data sets of diverse type, areal coverage, and spatial resolution, but also rapidly evolving digital mapping technologies. Though the modern geologic mapping process yields innovative products, robust data sets and mapping technologies tend to complicate the timeliness of map publication (which is critical due to ongoing data releases). Such complications can be minimized by advancing digital mapping procedures, adhering to a single map base (treating other data sets as supplemental), and encouraging community discussion over the life of a project. For planetary bodies in particular, geologic maps commonly represent a temporal snapshot of a surface because they are based on available information at a time when new data is often still being acquired. Increased data (and the observations made therein) should identify the limitations or shortcomings of previous maps and offer improvements. In addition to “classical” quad-based mapping, the abundance and diversity of data sets have afforded an increase in comparative mapping projects, including multi-scale, non-contiguous, cross-body, and/or compositional maps. Now more than ever, mappers must be not only cognizant of all facets of the mapping process but also responsible for performing detailed tasks in parallel that were previously performed in series.