Integrating GPR and CCRI techniques: Implications for the identification and mapping of ground ice on Mars

Abstract

Background: Since the early flyby missions of the 1970s, the study of Mars has largely focused on understanding the role of water (liquid or solid) in the geological evolution of the planet as well as its potential to support biotic activity. Data generated by the Mars Odyssey neutron and gamma ray spectrometers indicate large reservoirs of hydrogen (possibly H2O ice) in the near surface of Mars at latitudes greater than 50°. Additionally, Viking Orbiters and the Mars Orbiter Camera have revealed numerous landforms, possibly related to ground ice and permafrost processes (e.g., polygonal terrain, pingo-like mounds, thermokarst depressions, debris-aprons, and rock glacier-like features). However, despite observational evidence, an accurate identification and mapping of near-surface ground ice remains an open research question. Recently, the use of geophysical methods for investigating the Martian subsurface has witnessed growing interest among planetary scientists. Research involving the design and testing of geophysical instruments has focused primarily on Ground Penetrating Radar (GPR) and, to a lesser extent, seismic sounding, Time Domain Electromagnetic and Surface Nuclear Magnetic Resonance sounding. Approach: The purpose of this study is to investigate the occurrence of ground ice in an area analogous to what may be found on Mars, the ice cored terrain surrounding Athabasca Glacier, Alberta, Canada; and to examine the combined applicability of two geophysical methods such as GPR and Capacitively Coupled Resistivity Imaging (CCRI) in the investigation of the ice-rich Martian environment. Results and Implications: Our results show that GPR and CCRI techniques effectively complement each other by resolving different characteristics of the subsurface. While GPR clearly showed the subsurface structures and interfaces, CCRI provided diagnostic information about the subsurface lithologies. The two main implications of this combined application for the exploration Mars are: (a) it improves the ability to identify and map Martian ground ice; and, (b) it produces a more accurate description of the subsurface properties.