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Investigating the Extent of Bladed Terrain on Pluto via Photometric Surface Roughness.

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Title: Investigating the Extent of Bladed Terrain on Pluto via Photometric Surface Roughness.
Authors: Mishra, I.1 (AUTHOR) ishan.mishra@jpl.nasa.gov, Dhingra, R.1,2 (AUTHOR), Buratti, B. J.1 (AUTHOR), Seignovert, B.3 (AUTHOR), White, O. L.4,5 (AUTHOR)
Source: Journal of Geophysical Research. Planets. Jul2025, Vol. 130 Issue 7, p1-11. 11p.
Subject Terms: *Methane hydrates, *Erosion, Pluto (Dwarf planet), Surface roughness, Scientific expeditions, Photogrammetry, Planetary crusts
Company/Entity: United States. National Aeronautics & Space Administration , New Horizons (Spacecraft)
Abstract: NASA's New Horizons spacecraft discovered fields of sub‐parallel sets of steep ridges situated in the high‐altitude, low‐latitude regions in Pluto's encounter hemisphere called "bladed terrain." Thought to be formed due to sublimational erosion of methane ice, bladed terrain represents an active response of Pluto's landscape to current and past climates. The observation of a strong methane signature within the low latitudes of Pluto's non‐encounter hemisphere points to the possibility that this terrain type is also present there. To test this hypothesis, in the absence of high resolution images of Pluto's non‐encounter hemisphere, we employ photometric analysis of the methane rich regions. We specifically focus on determining the macroscopic surface roughness in selected images, whose photometric‐effect can be apparent even in low‐resolution images. We employ the "crater‐roughness" photometric model of Buratti and Veverka (1985, https://doi.org/10.1016/0019‐1035(85)90094‐6), which assumes that the surface is covered with parabolic depressions defined by a depth‐to‐radius ratio parameter q $q$ (higher q $q$ values correspond to rougher surfaces). Despite the high uncertainty in the retrieved roughness values from our analysis, we can safely conclude that the hypothesized bladed terrain region on the non‐encounter hemisphere of Pluto is very rough (q=0.47−0.11+0.10 $q=0.4{7}_{-0.11}^{+0.10}$, 2σ $\sigma $), with the median roughness more than twice that of other broad regions of Pluto studied in this work, including the encounter‐hemisphere bladed terrain region (q=0.21−0.18+0.08 $q=0.2{1}_{-0.18}^{+0.08}$, 2σ $\sigma $). Plain Language Summary: NASA's New Horizons spacecraft discovered "bladed terrain," which are bowl‐shaped depressions with blade‐like spires around the edge that rise several hundreds of meters. Bladed terrain is thought to be formed due to sublimation of methane ice. Although New Horizons could not take high spatial‐resolution images of the non‐encounter side of Pluto, the spectrometer LEISA found signatures of methane in vast, high‐altitude regions here as well, where bladed terrain might also be present. To test this hypothesis, we study the photometry of images of Pluto, that is, how the intensity of reflected sunlight changes with changing incidence and emission angles of light‐rays across various regions on Pluto's surface. We especially focus on the effects of the roughness of a given region, as it characteristically alters its photometric properties. Despite the high uncertainty in the retrieved roughness values from our analysis, we can safely conclude that the hypothesized bladed terrain region on the non‐encounter hemisphere of Pluto is very rough, with the median roughness around twice that of the encounter‐hemisphere bladed terrain region and six times that of the Sputnik Planitia, the massive basin (or "Pluto's heart") which is visibly devoid of features of the scale of bladed‐terrain. Key Points: We analyze the reflectance behavior of hypothesized bladed terrain regions on the non‐encounter side of Pluto using New Horizons dataPhotometry can probe effects of surface roughness for scales down to sizes on the order of surface particles (tens of microns in diameter), and help study the poorly imaged regions of a planetWe find the hypothesized bladed terrain regions to be relatively rough as compared to other areas of Pluto, indicating widespread sublimational erosion of methane‐ice on Pluto [ABSTRACT FROM AUTHOR]
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Description
Abstract:NASA's New Horizons spacecraft discovered fields of sub‐parallel sets of steep ridges situated in the high‐altitude, low‐latitude regions in Pluto's encounter hemisphere called "bladed terrain." Thought to be formed due to sublimational erosion of methane ice, bladed terrain represents an active response of Pluto's landscape to current and past climates. The observation of a strong methane signature within the low latitudes of Pluto's non‐encounter hemisphere points to the possibility that this terrain type is also present there. To test this hypothesis, in the absence of high resolution images of Pluto's non‐encounter hemisphere, we employ photometric analysis of the methane rich regions. We specifically focus on determining the macroscopic surface roughness in selected images, whose photometric‐effect can be apparent even in low‐resolution images. We employ the "crater‐roughness" photometric model of Buratti and Veverka (1985, https://doi.org/10.1016/0019‐1035(85)90094‐6), which assumes that the surface is covered with parabolic depressions defined by a depth‐to‐radius ratio parameter q $q$ (higher q $q$ values correspond to rougher surfaces). Despite the high uncertainty in the retrieved roughness values from our analysis, we can safely conclude that the hypothesized bladed terrain region on the non‐encounter hemisphere of Pluto is very rough (q=0.47−0.11+0.10 $q=0.4{7}_{-0.11}^{+0.10}$, 2σ $\sigma $), with the median roughness more than twice that of other broad regions of Pluto studied in this work, including the encounter‐hemisphere bladed terrain region (q=0.21−0.18+0.08 $q=0.2{1}_{-0.18}^{+0.08}$, 2σ $\sigma $). Plain Language Summary: NASA's New Horizons spacecraft discovered "bladed terrain," which are bowl‐shaped depressions with blade‐like spires around the edge that rise several hundreds of meters. Bladed terrain is thought to be formed due to sublimation of methane ice. Although New Horizons could not take high spatial‐resolution images of the non‐encounter side of Pluto, the spectrometer LEISA found signatures of methane in vast, high‐altitude regions here as well, where bladed terrain might also be present. To test this hypothesis, we study the photometry of images of Pluto, that is, how the intensity of reflected sunlight changes with changing incidence and emission angles of light‐rays across various regions on Pluto's surface. We especially focus on the effects of the roughness of a given region, as it characteristically alters its photometric properties. Despite the high uncertainty in the retrieved roughness values from our analysis, we can safely conclude that the hypothesized bladed terrain region on the non‐encounter hemisphere of Pluto is very rough, with the median roughness around twice that of the encounter‐hemisphere bladed terrain region and six times that of the Sputnik Planitia, the massive basin (or "Pluto's heart") which is visibly devoid of features of the scale of bladed‐terrain. Key Points: We analyze the reflectance behavior of hypothesized bladed terrain regions on the non‐encounter side of Pluto using New Horizons dataPhotometry can probe effects of surface roughness for scales down to sizes on the order of surface particles (tens of microns in diameter), and help study the poorly imaged regions of a planetWe find the hypothesized bladed terrain regions to be relatively rough as compared to other areas of Pluto, indicating widespread sublimational erosion of methane‐ice on Pluto [ABSTRACT FROM AUTHOR]
ISSN:21699097
DOI:10.1029/2024JE008554