Hierarchical clustering of pit crater chains on Venus

Abstract

Composed of a series of circular to elliptical bowl-shaped depressions, pit crater chains are common on the surface of many of our solar system’s terrestrial planets and moons. Using Magellan synthetic aperture radar (SAR) images, four areas of Venus are examined in which a total of 354 pit crater chains are found: Ganiki Planitia (180°E–210°E, 25°N–50°N), Ulfrun Regio (200°E–240°E, 0°N–25°N), Themis Regio (270°E–300°E, 25°S–40°S), and Idunn Mons (205°E–225°E, 35°S–55°S). A study of the distribution of these pit crater chains at regional and local scales reveals hierarchical clustering. On a regional scale, pit crater chain clusters are associated with graben–fissure systems that are radiating (associated with volcano-tectonic features), circumferential (associated with coronae), and linear (with uncertain volcano-tectonic genesis). At a local scale, pit crater chains are found with marked restriction to particular portions of graben–fissure systems. We conclude that this hierarchical clustering is an indication that both an extensional process and a lithological control contribute to the formation of pit crater chains. Specifically, we propose that pit crater chain formation on Venus occurs in poorly welded volcaniclastic material (e.g., shield plains material unit) that has been crosscut by graben–fissure system(s). Only portions of the shield plains material unit may have sufficient thickness of volcaniclastic material, thus explaining the lack of a co-extensive relationship. Additionally, pit crater chains in other map units may be explained by shallow burial of the volcaniclastic material.

Fundamental Science and Engineering Questions in Planetary Cave Exploration

“…( 2022 ), whereby a solar system wide inventory was conducted to identify past speleogenic processes and resultant products; they reported nine speleogenic processes on 15 planetary bodies and SAPs on 11 bodies. For example, Enceladus (Porco et al., 2014 ), Titan (Malaska et al., 2020 ; Wynne et al., 2022 ), and other icy bodies support active speleogenesis associated with tectonic activity and dissolution, while Mercury (Jozwiak et al., 2018 ), Venus (Davey et al., 2013 ), and Io (Wynne et al., 2022 ) likely support caves within tectonic and volcanic terrains (Wynne et al., 2022 and additional references therein). Additionally, fissures responding to seasonal processes may occur in subpolar regions of Mars, with potential subglacial networks of brine‐filled cavities (e.g., Lauro et al., 2021 ).…”

Mapping of Geologic Structures in the Niobe‐Aphrodite Map Area of Venus: Unraveling the History of Tectonic Regime Change

“…Some fractures transition to pit chains, sharply defined depressions or linear arrays of pits that likely represent regions marked by subsurface excavation. These troughs are the surface expression of dilatational faults or dikes (Bleamaster & Hansen, ; Davey et al, ; Ferrill et al, ; Grosfils & Head, ; Okubo & Martel, ; Schultz et al, ) or stoping features lacking associated crustal extension (Cushing et al, ). Pits or pit chains can be considered primary structures or secondary structures, depending on the question at hand; pits are primary structures relative to pit‐related materials, yet they may be secondary structures relative to the units they cut or are emplaced within.…”

Thermal and Illumination Environments of Lunar Pits and Caves: Models and Observations From the Diviner Lunar Radiometer Experiment

“…Lava tube and cave are used interchangeably throughout the text. Collapse pits have been found on every major rocky body of the inner solar system (Davey et al., 2013; Haruyama et al., 2009; Kerber et al., 2011; Okubo & Martel, 1998; Wyrick et al., 2004). However, distinct overhangs have only been observed on Earth and the Moon.…”