Investigation of topographic and object characteristics of terrestrial impact craters based on remote sensing approaches

Abstract

Impact craters are important landforms formed by the collision of hypervelocity celestial objects such as asteroids or comets with the planet’s surface. The formation of impact craters involves three main stages including contact and compression, excavation, and modification that reshape the Earth’s crust and leave the circular-shaped topographic imprints on the planet’s surface. The processes involved in crater formation depend on several factors including the energy of the impactor, target lithology, and rheological condition of target rocks that lead to small or large impact structures. Impact cratering has been found as an important geological record that assists in quantifying impact flux in geological time scale, and reveals the evolution of planets, and other celestial objects. Impact crater science helps also to date the geological phenomena, and come up with a chronological sequence of planetary events. In addition, the impact cratering induces an impressive geological landform that plays a great role in geo-tourism development and geological heritage. Therefore, a substantial effort is made to explore and describe those remarkable and impressive landscapes based on various techniques such as remote sensing, geophysics, and geological surveys. The exploration of impact craters included reconnaissance and conclusive stages. The stage of reconnaissance involves mainly remote sensing and geophysical surveys to describe the morphology of potential impact crater candidates and serve as a guide to the final conclusive stage. The conclusive stage aimed at identifying the mega-scales and macroscale evidence such as shatter cones and planar deformation features in shocked quartz via extensive geological surveys and laboratory experiments. Various techniques and impact crater detection algorithms are continuously developed to improve impact crater detection based on remote sensing data. Several automatic approaches have been mostly focused on extraterrestrial planets; however, few trials have been performed to detect terrestrial impact craters, were limited to few numbers in narrow diameters size. These limited the exploration of impact crater candidates in remote areas or areas of limited access. The morphological expressions of extraterrestrial impact craters are more exposed to the surface which ease automatic detection compared to the terrestrial craters because of active 2 geological conditions of Earth’s crust. In addition, most automatic crater detection algorithms that have been developed are based on pixels that might be easily affected by noise and have limitations in recognizing complex spatial features in heterogenous landscapes like Earth’s surface. To contribute to the terrestrial impact crater exploration and overcome the limitation of pixel-based image analysis, Object-Based Image Analysis (OBIA) was executed in this study expecting the formation of circular segments around the circular morphology of impact craters. The OBIA is more convenient in the tasks of identifying or analyzing the relationship of spatial features such as landscapes, and urban mapping. The objects or segments of targeted features are formed via the multiresolution segmentation algorithm, where the size of the object depends on user-defined scale parameters. The global 30m/pixel resolution Shuttle Radar Topography Mission Digital Elevation Model (SRTM DEM) was the source of raster topography data in this study. On the other hand, the impact crater morphometric studies divide the impact craters in three types including simple, complex, and transitional (basin). The pristine simple craters are indicated by sharp bowl-shaped depressions with a diameter size of ~ 2 km for sedimentary and ~4 km for crystalline. Typical pristine complex craters are mainly indicated by terraced wall, the central peak in crater floor and the size varies widely from around ~ 4 km in diameter. However, the transition craters have relatively flat floor bases compared to the simple craters and lack central pick rings. The transitional diameter is not an abrupt change, it even varies from one planetary body to another because of the gravitation force and rheology of target rocks. Presently, the size of known transitional terrestrial craters varies from 3 – 10 km. Discovering impact craters is a dynamic process, every decade several new impact craters are discovered, however, recognizing impact crater types is not straightforward in geological active conditions like Earth’s crust, and post-impact craters processes including mass transport of crater wall, and sediment deposition layers usually confine central uplifts. The case example is Jeokjung Chogye Basin (JCB) in the Korean peninsula, South Korea, it has been recently confirmed as an impact crater, but the crater type is still unclear. To investigate the buried central uplift a complex and cost-effective geophysics surveys such as gravity, magnetic surveys, and drillings are mostly used to detect the densified peak rocks that emerge in sediment layers.