Layered mound, inverted channels and polygonal fractures from the Makgadikgadi pan (Botswana): Possible analogues for Martian aqueous morphologies

Uneven surface moisture as a driver of dune formation on ephemeral lake beds under conditions similar to the present day: A model‐based assessment from the Makgadikgadi Basin, northern Botswana

“…Similar intra‐basin crescentic landforms have also been identified on the surface of Mars (Franchi et al, 2014; Pondrelli et al, 2015, 2019; Pozzobon et al, 2019), and knowledge of their formative mechanisms may help landscape interpretation in this extra‐planetary context (e.g. Bourke & Goudie, 2009; Franchi et al, 2020). One region, the Makgadikgadi Basin of northern Botswana, has received notable long‐term interest and investigation into the formation of these landforms (e.g.…”

“…Some form distinct arcuate‐shaped mounds, whilst others are more elongate in form. Previous investigations suggest they are primarily composed of poorly sorted, very fine to medium sand‐sized particles (Burrough et al, 2012; Burrough et al, in preparation; Franchi et al, 2020). Their vegetated surfaces, which can sustain a dense covering of halotrophic grasses (predominantly Odyssea paucinervis and Sporobolus ioclados ), make these features visibly distinct in remotely sensed imagery, in contrast to the generally de‐vegetated and inhospitably saline conditions of the pan floor (Burrough et al, 2012).…”

“…Here, scientific interest in the crescentic sand mounds has spanned half a century and the unresolved debate concerning their origins has become increasingly lively in recent years (e.g. Burrough & Thomas, 2013; Burrough et al, 2012; Franchi et al, 2020; McFarlane & Long, 2015). In this paper we take aspects of these previous empirical studies to inform a model‐based approach that tests the feasibility and robustness of a new theory of formation; ‘the sticky mound hypothesis’.…”

“…(F) Mound field in the southeastern sector of the Firsoff crater, Mars (Hirise ESP_020679_1820). Images modified from Burrough et al (2012) and Franchi et al (2014, 2020) [Color figure can be viewed at wileyonlinelibrary.com]…”

“…In an alternative assessment, using Google Earth imagery, McFarlane and Long (2015) inferred the features to be spring mounds formed by ongoing discharge of potable groundwater and sediment, with their initiation related to a pre‐Quaternary lake. Most recently, Franchi et al (2020) used electric resistivity tomography (ERT) to assess water‐upwelling processes and found the presence of a highly resistive body (the mound sediments) over a low‐resistivity body, possibly linked to a capillary fringe or very shallow groundwater table within the lake‐bed sediments. Franchi et al (2020) also reached no firm conclusion but suggested the ‘layered mounds’ were remnants of the lake's former shoreline, the result of progressive erosion by surface runoff and wind deflation of relict, bedded strandlines.…”