Hydrothermal activity recorded in post Noachian‐aged impact craters on Mars

Stuart M R Turner,Bethany L Ehlmann,Stephen Grebby,John C Bridges

doi:10.1002/2015je004989

Stuart M R Turner, Bethany L Ehlmann + Show 2 more

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https://doi.org/10.1002/2015je004989

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Abstract

AbstractHydrothermal systems have previously been reported in ancient Noachian and Hesperian‐aged craters on Mars using CRISM but not in Amazonian‐aged impact craters. However, the nakhlite meteorites do provide evidence of Amazonian hydrothermal activity. This study uses CRISM data of 144 impact craters of ≥7 km diameter and 14 smaller craters (3–7 km diameter) within terrain mapped as Amazonian to search for minerals that may have formed as a result of impact‐induced hydrothermal alteration or show excavation of ancient altered crust. No evidence indicating the presence of hydrated minerals was found in the 3–7 km impact craters. Hydrated minerals were identified in three complex impact craters, located at 52.42°N, 39.86°E in the Ismenius Lacus quadrangle, at 8.93°N, 141.28°E in Elysium, and within the previously studied Stokes crater. These three craters have diameters 20 km, 62 km, and 51 km. The locations of the hydrated mineral outcrops and their associated morphology indicate that two of these three impact craters—the unnamed Ismenius Lacus Crater and Stokes Crater—possibly hosted impact‐induced hydrothermal systems, as they contain alteration assemblages on their central uplifts that are not apparent in their ejecta. Chlorite and Fe serpentine are identified within alluvial fans in the central uplift and rim of the Ismenius Lacus crater, whereas Stokes crater contains a host of Fe/Mg/Al phyllosilicates. However, excavation origin cannot be precluded. Our work suggests that impact‐induced hydrothermalism was rare in the Amazonian and/or that impact‐induced hydrothermal alteration was not sufficiently pervasive or spatially widespread for detection by CRISM.

Highlights

Understanding the history, nature, and occurrence of hydrated minerals in the Martian crust is key to identifying potential past habitable environments
For the unnamed impact crater in the Ismenius Lacus quadrangle shown in section 3.1, it is possible that the observed Fe/Mg phyllosilicates formed within the central uplift and were subsequently excavated, transported, and deposited by the processes that led to the formation of the gullies and alluvial fans—by a process
This study conducted CRISM analysis of 144 craters of ≥7 km diameter in terrains mapped as Amazonian or Amazonian-Hesperian on Mars

Summary

Introduction

Understanding the history, nature, and occurrence of hydrated minerals in the Martian crust is key to identifying potential past habitable environments. Remote sensing studies using the OMEGA (Observatoire pour la Minéralogie, l’Eau, les Glaces et l’Activité) and CRISM (Compact Reconnaissance Imaging Spectrometer for Mars) visible to infrared spectrometers on MEX and MRO, respectively, have identified phyllosilicates predominantly in ancient Noachian era terrains of Mars [Poulet et al, 2005; Mustard et al, 2008; Ehlmann et al, 2011a; Carter et al, 2013] These studies, along with others [e.g., Marzo et al, 2010; Mangold et al, 2012; Osinski et al, 2013], have reported evidence of hydrothermal minerals associated with numerous craters formed in the Noachian and Hesperian terrains, mostly via excavation of older altered material, but with impact-induced hydrothermalism occurring in a small number of craters.

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