Groundwater activity inferred from potential clastic dikes in Eberswalde crater, Mars

Fluvial and sedimentary deposits on Mars provide key evidence of surface water activity in geologic times. On the contrary, the distribution and characteristics of Mars’ past groundwater activity remain poorly understood, limiting our ability to reconstruct the early Mars climate regimes. Eberswalde crater, known for hosting the most well-preserved deltaic deposit on Mars, exhibits meandering lobes of inverted channels [1,2], as evidence for sustained fluvio-lacustrine activity in a standing body of water [2-4]. In this study, we present a detailed analysis of the morphology, mineralogy, and stratigraphy of vein-like structures within Eberswalde crater using high-resolution imagery data (HiRISE and CTX). We identified three major morphological types of vein-like structures. Type II structures showed varying widths between 1.5 m and 4 m. Through manual co-registration to the CRISM data, we identified a correlation between the high-albedo linear feature and a clay-bearing spectral signature which matches well with the spectral features in Eberswalde delta sediment. We propose that these features were clastic dikes formed due to groundwater activity, before or at the same time as the formation of the deltaic deposits. Stratigraphic relationships between the identified structures and the mapped geologic units [5-6] suggest the top unit of the delta is relatively young. The morphometry and spatial distribution of the clastic dikes offer valuable constraints on the flux and velocity of ancient groundwater in this region.

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