Comparison of central pit craters on Mars, Mercury, Ganymede, and the Saturnian satellites

Abstract

We report on the first results of a large‐scale comparison study of central pit craters throughout the solar system, focused on Mars, Mercury, Ganymede, Rhea, Dione, and Tethys. We have identified 10 more central pit craters on Rhea, Dione, and Tethys than have previously been reported. We see a general trend that the median ratio of the pit to crater diameter (Dp/Dc) decreases with increasing gravity and decreasing volatile content of the crust. Floor pits are more common on volatile‐rich bodies while summit pits become more common as crustal volatile content decreases. Uplifted bedrock from below the crater floor occurs in the central peak upon which summit pits are found and in rims around floor pits, which may or may not break the surface. Peaks on which summit pits are found on Mars and Mercury share similar characteristics to those of nonpitted central peaks, indicating that some normal central peaks undergo an additional process to create summit pits. Martian floor pits do not appear to be the result of a central peak collapse as the median ratio of the peak to crater diameter (Dpk/Dc) is about twice as high for central peaks/summit pits than Dp/Dc values for floor pits. Median Dpk/Dc is twice as high for Mars as for Mercury, reflecting differing crustal strength between the two bodies. Results indicate that a complicated interplay of crustal volatiles, target strength, surface gravity, and impactor energy along with both uplift and collapse are involved in central pit formation. Multiple formation models may be required to explain the range of central pits seen throughout the solar system.

Observations From a Global Database of Impact Craters on Mercury With Diameters Greater than 5 km

“…When we examine the distribution of crater morphologies, there are definitely nonrandom distributions of different morphologies within a diameter bin. Our results corroborate nonrandom spatial distributions of hollows (Blewett et al, ; Thomas et al, ), pits attributable to explosive volcanism (Thomas et al, ), and central‐crater pits that other researchers have observed (Barlow et al, ; Xiao & Komatsu, ). We add to these our observations of crater central structures for craters with D ≈ 100 km (Figure ), particularly the distinction between craters with some form or ringed peak and those with a single central structure or multiple unorganized central structures.…”

“…On Mars and some of the outer‐planet satellites (e.g., Barlow et al, ; Barlow & Bradley, ; Schenk, ; Xiao & Komatsu, ) a small circular central‐pit either in place of or atop a crater's central peak has been identified as a common crater landform that comprises a large percentage (>10%) of well‐preserved craters in certain diameter ranges. On Mercury a small number of craters have pits analogous to those atop a central peak (central‐structure summit pit, 21 craters) or on the crater floor in place of central peak (central‐structure floor pit, 1 crater).…”

Formation of Central Pits in Impact Craters on Mars: A Statistical Investigation of Proposed Mechanisms

“…Previous investigations have described and investigated the relationships of spatial distribution and target properties (including rock type) with different types of impact craters, including different types of central pit craters (e.g., Barlow, 2011;Barlow, 2017). Both summit and floor central pit craters span the midlatitudes and all longitudes of Mars, although there is a dearth of both CPCs and central peak craters on Tharsis and in Hellas and Argyre basins (see below, Figure 3).…”

“…the conclusion that a component of structural uplift is likely required for central pit formation (Bray et al, 2009;Barlow et al, 2017).…”

“…• Table S1 • Table S2 • Table S3 • Table S4 • Table S5 ( Barlow et al, 2017;Xiao & Komatsu, 2013), on Ceres (Russell, 2015;Zeilnhofer & Barlow, 2018), and the Saturnian satellites of Rhea, Dione, and Tethys (Barlow et al, 2017, and citations therein). Multiple formation models for CPCs have been proposed (section 2).…”