Short-term erosion rate of impact craters using radar data: Implications for their morphology

Erosion poses several challenges for studying terrestrial impact craters, as it results in subdued morphology. Erosion not only erases crater morphology but also leads to disagreements among geoscientists on morphological aspects. Ramgarh Crater, in the north-western India, is an example of such a crater with notable contentions pertaining to its type and morphology as a few studies point towards the denudation of the outer rim of a complex crater of 10 km apparent diameter. Meanwhile, the simple crater theory argues for a rim-to-rim diameter of ∼2.4 km. In this study, for the first time, an advanced radar data analysis, called the Persistent Scatterer Interferometric Synthetic Aperture Radar (PSInSAR), is applied to quantitatively assess the short-term erosion rate of Ramgarh Crater, for the period between 2017 and 2022. PSInSAR is a microwave based remote sensing method that measures the rate and direction of ground surface movement. This method enabled a more robust analysis of erosion processes within and around the crater and facilitated a comprehensive understanding of its morphological features. Our study using PSInSAR could not identify any significant erosion in the elevated relict structure (considered as the rim of the simple crater) (mean velocity of −0.83 mm/yr) whereas other zones, including the 10 km apparent diameter, are characterized by similar erosion (mean velocity between −2.02 to −6.9 mm/yr) because of agricultural practice, badland topography and active river bed erosion. Additionally, field observations from multiple traverses and visual interpretation of high-resolution remotely sensed images across the 10 km apparent diameter did not yield any morphological evidences favouring a raised rim. Based on these findings, Ramgarh can be classified as a simple crater with the relict structure of 2.4 km rim-to-rim diameter, being the elevated rim. Thus, the implementation of PSInSAR has facilitated a comprehensive examination of the crater's morphology and has conclusively resolved a significant debate surrounding Ramgarh Crater. As a result, the PSInSAR technique emerges as a valuable tool for resolving various geological conundrums, especially in the field of planetary science.