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Pluto Geologic Map: Use of Crater Data to Understand Age Relationships.

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Title: Pluto Geologic Map: Use of Crater Data to Understand Age Relationships.
Authors: Singer, K. N.1 (AUTHOR) kelsi.singer@swri.org, White, O. L.2 (AUTHOR), Greenstreet, S.3,4 (AUTHOR), Moore, J. M.5 (AUTHOR), Williams, D. A.6 (AUTHOR), Lopes, R. M. C.7 (AUTHOR)
Source: Journal of Geophysical Research. Planets. Jan2025, Vol. 130 Issue 1, p1-16. 16p.
Subject Terms: Kuiper belt, Geological maps, Geological mapping, Sequence stratigraphy, Solar system, Impact craters, Lunar craters
Abstract: Pluto's surface displays a wide variety of geologic units from smooth plains to extremely rugged mountainous expanses. These terrains range in age from young, actively resurfaced regions (no observable craters even in the highest‐resolution New Horizons images) to old, heavily cratered, eroded regions. Here we expand upon the crater data analysis and the independent crater data set used in the production of a 1:7M scale geologic map of Pluto that is to be published by the United States Geologic Survey (USGS). We present both relative ages based on crater spatial density (number of craters in a given size bin per km2) and quantitative ages (e.g., 2 Ga) using the estimated impactor flux onto Pluto. The techniques presented here were developed specifically for the information available from a USGS geologic map, where smaller craters are mapped as points only (no specific diameter information per crater). We developed a new type of visualization, called a distributed R‐plot, to understand the relative ages of the geologic units. The uncertainties in the current knowledge of the Kuiper belt populations and impactor flux at Pluto propagate to large uncertainties in the estimated quantitative ages (∼a factor of two). However, both relative and quantitative ages from crater analysis are valuable tools in developing the sequence of geologic events. Pluto has large areas of crater‐free young terrains (13 units making up ∼27% of mapped higher‐resolution surface area) with widely varying morphologies, indicating a variety of resurfacing mechanisms, both exogenic and endogenic, likely active in Pluto's recent past or present. Plain Language Summary: Geologic maps highlight different types of units across a body and can be useful for observing patterns and understanding the geologic history of a body. Craters form continuously across Pluto from the bombardment of other smaller Kuiper belt objects. Thus, a surface with fewer craters has likely been resurfaced. The resurfacing event could partially or completely erase craters, could happen at a more distinct point in time, or be a long‐term process. Each of these scenarios leaves different geological clues, both in the number of craters and their erosion states. A large fraction (∼30%) of the surface of Pluto observed in detail by the New Horizons spacecraft (Plutos "near‐side") is completely devoid of craters, indicating that these are very young surfaces and implying relatively recent geologic activity on Pluto. Additionally, the impact rates on Pluto have been estimated and we can get a rough idea of when in the Solar System's ∼4.5 billion year history the surfaces on Pluto likely formed. Key Points: We developed crater analysis techniques with specific applications for determining stratigraphic sequences on United States Geologic Survey geologic mapsPluto has a wide variety of both younger and older terrain types, implying ongoing activity and a diverse geologic historyYoung, crater‐free, areas with widely varying geomorphology make up a large fraction, about 30%, of Pluto's near‐side [ABSTRACT FROM AUTHOR]
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Abstract:Pluto's surface displays a wide variety of geologic units from smooth plains to extremely rugged mountainous expanses. These terrains range in age from young, actively resurfaced regions (no observable craters even in the highest‐resolution New Horizons images) to old, heavily cratered, eroded regions. Here we expand upon the crater data analysis and the independent crater data set used in the production of a 1:7M scale geologic map of Pluto that is to be published by the United States Geologic Survey (USGS). We present both relative ages based on crater spatial density (number of craters in a given size bin per km2) and quantitative ages (e.g., 2 Ga) using the estimated impactor flux onto Pluto. The techniques presented here were developed specifically for the information available from a USGS geologic map, where smaller craters are mapped as points only (no specific diameter information per crater). We developed a new type of visualization, called a distributed R‐plot, to understand the relative ages of the geologic units. The uncertainties in the current knowledge of the Kuiper belt populations and impactor flux at Pluto propagate to large uncertainties in the estimated quantitative ages (∼a factor of two). However, both relative and quantitative ages from crater analysis are valuable tools in developing the sequence of geologic events. Pluto has large areas of crater‐free young terrains (13 units making up ∼27% of mapped higher‐resolution surface area) with widely varying morphologies, indicating a variety of resurfacing mechanisms, both exogenic and endogenic, likely active in Pluto's recent past or present. Plain Language Summary: Geologic maps highlight different types of units across a body and can be useful for observing patterns and understanding the geologic history of a body. Craters form continuously across Pluto from the bombardment of other smaller Kuiper belt objects. Thus, a surface with fewer craters has likely been resurfaced. The resurfacing event could partially or completely erase craters, could happen at a more distinct point in time, or be a long‐term process. Each of these scenarios leaves different geological clues, both in the number of craters and their erosion states. A large fraction (∼30%) of the surface of Pluto observed in detail by the New Horizons spacecraft (Plutos "near‐side") is completely devoid of craters, indicating that these are very young surfaces and implying relatively recent geologic activity on Pluto. Additionally, the impact rates on Pluto have been estimated and we can get a rough idea of when in the Solar System's ∼4.5 billion year history the surfaces on Pluto likely formed. Key Points: We developed crater analysis techniques with specific applications for determining stratigraphic sequences on United States Geologic Survey geologic mapsPluto has a wide variety of both younger and older terrain types, implying ongoing activity and a diverse geologic historyYoung, crater‐free, areas with widely varying geomorphology make up a large fraction, about 30%, of Pluto's near‐side [ABSTRACT FROM AUTHOR]
ISSN:21699097
DOI:10.1029/2024JE008533