Multi-scale Morphology of Fluidized Ejecta Blankets and their Spectral Counterpart

Studying the geomorphology of crater ejecta at Martian mid- to high-latitudes is essential for understanding how impact-generated flows and debris patterns indicate subsurface ice or water at the time of impact. By analyzing ejecta morphologies, such as rampart structures, lobate flows, and layered deposits, we can reconstruct the distribution and abundance of volatiles in the Martian subsurface. These morphological observations provide the basis for stratigraphic correlations and spectroscopic analyses, enabling more precise quantification of past and present water-ice concentrations in the upper crust.  Our study focuses on a fresh crater (43.81N, 301.53E) located roughly 225km NE of Timoshenko crater, in Tempe Terra. By using Digital Terrain Models (DTMs) at different scales (CTX at 6m ppx and HiRISE at 0.3m ppx) we map the different ejecta blankets that comprise this crater and classify it based on their topography and shape. 

We created DTMs using the Ames Stereo Pipeline (ASP, [1]) and two stereopairs per instrument (CTX J14_050126_2236_XN_43N058W and P12_005807_2238_XI_43N058W, HiRISE ESP_059370_22401 and ESP_077029_2240), aligned to overlying MOLA data from PDS ([2]), and then projected within a GIS software (QGIS, v3.40.5), which helps in DTM manipulation, visualization, and topographic studies of the ejecta layers and their subsequent plotting, while using different data formats. 

From CTX imagery, we recognize 2 ejecta layers: one proximal to the crater (500m from crater rim), with a slope of 20˚ and smoother topography, which ends in a small (~10m) edge step; and a second more distal, showing a radial lobate pattern exuding from the crater, composed of rougher materials, with little to no slope (~3˚).

Following [3]’s classification, we classify this as a type 2 (double ejecta facies) or type 3 (multiple facies) crater. This uncertainty is related to the resolution limits of  CTX; it is difficult to determine whether the second ejecta layer is further subdivided into more layers, as the contacts become diffuse, and the more distal parts of it appear as isolated ejecta clusters, disconnected from the main facies, especially in the NW and SE margins. 

Our multi-scale morphological analysis of the crater will place it into context with its surroundings [4] and prepare for specific studies, such as the spectroscopic analysis of specific areas [5]. Using CTX DTMs as a basemap will provide a robust and smooth topography, which can be better interpreted and used for mapping; HiRISE will offer very high resolution, allowing a more robust identification of smaller features. The accurate development of DTMs at appropriate resolution is key and we will concentrate efforts on uncertainty analyses of these higher-level data products. We are applying these techniques into operational mission-driven scenarios like the Oxia Planum landing site of the ESA/ExoMars Rosalind Franklin Rover [5].

This work is funded by the Italian Space Agency (ASI) [Grant ASI-INAF n. 2023–3–HH.0].

References: [1] Beyer et al. (2018) ESS 5(9), 537-548; [2] Smith et al. (2001) JGR Journal of Geophysical Research: Planets 106.(E10); 2156-2202. [3] Mouginis-Mark (1979) JGR Solid Earth 84(B14), 8011-8022. [4] Rasmussen et al., (2025) GSA A&Ps 57(6), p. 4976. [5] Altieri et al. (2026), this conference.