A Map of Potential Topographic Anomalies on Venus

The most recent, highest-resolution, global estimate of the topography of Venus is the Global Topographic Data Record (GTDR), a gridded representation of the altimetry data from the Magellan space mission. This product is impaired by an occasional pattern; a series of visually striking topographic “pits,” often referred to as spuriously low values, which in many cases might be generating false topographic signatures. These generally arise from the incorrect identification of secondary, delayed power peaks in the individual altimeter records, which causes local topographic underestimations. There are many such “pits” across the GTDR, and they can lead to misinterpretation of geomorphological features. In this study, we describe GTDR data errors in detail and the situations in which they occur, and propose a method to classify spuriously low values across the entire product as potential anomalies. The method is based on the computation of the local altimeter ambiguity height around each pixel, modulated by an estimate of the relative elevation uncertainty between the pixel and the neighboring topography. We generate global maps of the potential anomalies, and find that up to 2.865% of the original product is impaired by them. They are concentrated in particular around rift systems and summit areas at low latitudes, and can be used to identify areas that would benefit from reprocessing the altimeter records. We argue that GTDR-supported geomorphological interpretations of surface features on Venus, in particular of chasmata, are susceptible to depth overestimation and cross-section distortion due to the accumulation of potential topographic anomalies.