A Reference Tool for Planetary Geoscience Synthesis: Index of Places

Scientific progress depends on stable reference systems in which previous results, observations, and data can be reliably identified, compared, and reused. In planetary geoscience, research often focuses on surface structures and units. These are used to infer present or past surface, atmospheric, and interior processes from shape, material properties, spatial distribution, age, or combinations of these attributes.  

A reliable register of surface entities is needed because no comprehensive, cross-catalog, ontology-oriented surface census of this kind currently exists for any planetary body. Such a system would address a basic question: what exists on the surface? More specifically, how can a planetary surface be represented as a set of spatially anchored, sometimes overlapping, scale-dependent entities of structures and units? A single item may share characteristics with different groups of other items, and those characteristics may be interpreted differently by different authors.

Planetary features have traditionally been organized through nomenclature. When recognized, they are named with descriptor terms based on morphology, displayed on maps and collected in lists and catalogs that served as reference data for research.

In recent decades, however, higher-resolution image and radar data have increased the number of identified surface features to a level where naming all of them has become impractical. Nomenclature remains useful for large, prominent, or unique features, but it is not used for geologic units or for the “uncountable” number of smaller features to receive proper names.

The Lunar Grid Reference system illustrates a parallel need for compact, systematic spatial identification. The Lunar Grid Reference System addresses a related but different problem: it provides compact spatial identifiers for grid cells rather than identifiers for geologic entities. (McClernan 2024, Navarre et al. 2026).

Nevertheless, these features still need to be identified, defined, and recorded. They must be traceable across papers and catalogs; otherwise, it becomes increasingly difficult to correlate the subjects of different studies. This problem is demonstrated by recent attempts to merge data from diverse sources, including geologic units (Ivanov and Head 2011), surface features (Gülcher et al. 2025), and raster data (Austin et al. 2026).

Useful analogies exist in astronomy. SIMBAD grew out of efforts to cross-identify astronomical objects and now provides basic data, cross-identifications, bibliography, and measurements for objects outside the Solar System (Heck and Egret 1987). The NASA/IPAC Extragalactic Database NED serves a similar role for extragalactic objects. Planetary surface features raise different difficulties, but the aim is similar: to connect multiple identifiers, geometries, classifications, and references to the same entity.

The Proposed Index of Places

The Index of Places (Hargitai 2026b) would assign unique IDs to identified planetary surface structures and units. It would link each entity to the catalogs in which it was listed, the geologic maps on which it was mapped, and, in time, the papers in which it was discussed. Its coverage could expand progressively.

The Index would first ingest features from existing catalogs, databases, and geologic maps. Each identifier would be associated with measured attributes, such as size and area; a polygon or polyline representing shape; a name, if the entity is named or listed in the Gazetteer; and links to papers that discuss or classify it. Different terms and classifications would be stored with their references.

The Index of Places would combine geologic maps, catalogs, and research literature into a developing ontology. Persistent identifiers (IDs) would serve as the primary anchor, while each entity could have one or more source-specific geometries.

A key question is what should count as an entity. The Index should distinguish between discrete surface features, mapped geologic units, feature groups, and other interpretive regions, while allowing links among them. A feature may contain subunits and one feature may also be part of another. Groups of features could also be handled collectively and individually through linked IDs.

Pilot Work

The first pilot of this Index has been completed: the Venus GIS (Hargitai 2016, 2026a), which combined most previously made feature catalogs and maps of Venus in an integration and data-preservation effort. This effort brought together datasets that had existed on private drives, in outdated formats, or in scanned, machine-unreadable catalogs.

This feature-based approach should now be transformed into a surface-location-based catalog: the Index of Places. When completed, it can be paired with raster datasets and incorporated into machine-learning systems, where it can supply training labels for pattern recognition. The Index may also be used to evaluate previous catalogs and estimate data confidence (e.g., Heyer et al. 2023).

At the same time, Foundation Models are being initialized for AI and Machine Learning applications (NASA 2025). This creates an opportunity to connect past mapping work with future AI infrastructure, forming a persistent reference basis for planetary geoscience.

 

References

Austin, T. J., O’Rourke, J. G., & Nelson, D. M. (2026).  https://doi.org/10.1029/2025EA004846

Hargitai, H. (2016).  DPS 48/EPSC 11 Meeting (Abstract #426.23). Pasadena, CA.

Hargitai, H. (2026a).  https://doi.org/10.5281/zenodo.18943246

Hargitai, H. I. (2026b).  MAPSIT April 2026  Abstract 6020

Heck, A., & Egret, D. (1987). SIMBAD, the CDS database. The Messenger, 48, 22–24.

Heyer, T., Iqbal, W., Oetting, A., Hiesinger, H., van der Bogert, C. H., & Schmedemann, N. (2023). https://doi.org/10.1016/j.pss.2023.105687

Ivanov, M. A., & Head, J. W. (2011).  https://doi.org/10.1016/j.pss.2011.07.008

McClernan, M. (2024).  https://doi.org/10.5066/P13YPWQD

NASA - (2025). Foundational Artificial Intelligence for the Moon and Mars (FAIMM) (ROSES-2025 Program Element C.12; Solicitation No. NNH25ZDA001N-FAIMM).  

Navarre, R., Almquist, Z., & Chase, R. (2026).  MAPSIT April 2026 Meeting  Abstract 6009

Pekala, M., Canal, G., Barham, S., Graziano, M. B., Trexler, M., Hamilton, L., Reilly, E., & Stiles, C. D. (2025).  arXiv. https://doi.org/10.48550/arXiv.2504.20125