Abstract

Mars’ polar caps are – depending on hemisphere and season - partially or totally covered with CO2 ice. Icy surfaces such as the polar caps of Mars behave differently from surfaces covered with rock and soil when they are irradiated by solar light. The latter absorb and reflect incoming solar radiation within a thin layer beneath the surface. In contrast, ices are partially transparent in the visible spectral range and opaque in the infrared. Due to this fact, the solar radiation can penetrate to a certain depth and raise the temperature of the ice or dust below the surface. This may play an important role in the energy balance of icy surfaces in the solar system, as already noted in previous investigations. We investigated the temperature profiles inside CO2 ice samples including a dust layer under Martian conditions. We have been able to trigger dust eruptions, but also demonstrated that these require a very narrow range of temperature and ambient pressure. We discuss possible implications for the understanding of phenomena such as arachneiform patterns or fan shaped deposits as observed in Mars’ southern polar region.

Highlights

  • The Martian polar caps are currently the only assured naturally occurring carbon dioxide ice deposits in the inner solar system and they are one of the most active geological features on the Martian surface

  • While at the northern polar cap the CO2 ice sublimes during the summer season uncovering a base of H2O ice, there is a perennial and seasonal CO2 ice deposit at the southern polar cap (Bibring et al, 2004; Langevin et al, 2005)

  • Based on work by Kaufmann et al (2006), who investigated the solid state greenhouse effect on various materials such as clear compact H2O ice and glass beads with and without absorbing layers, we investigated the behaviour of CO2 ice under Martian conditions in a series of experiments

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Summary

Introduction

The Martian polar caps are currently the only assured naturally occurring carbon dioxide ice deposits in the inner solar system and they are one of the most active geological features on the Martian surface. A possible explanation for the formation of these geomorphic features is the so-called ‘solid-state greenhouse effect’, further on denoted as SSGE, a phenomenon similar to the atmospheric greenhouse effect (Brown and Matson, 1987; Fanale et al, 1990): sunlight can penetrate the CO2 ice layer down to a dust deposit at depth where the radiation is absorbed, with the heat increase leading to sublimation of the CO2 ice on the boundary between the ice layer and the underlying dark material. Based on work by Kaufmann et al (2006), who investigated the solid state greenhouse effect on various materials such as clear compact H2O ice and glass beads with and without absorbing layers, we investigated the behaviour of CO2 ice under Martian conditions in a series of experiments These experiments may contribute to our understanding of the phenomena observed on Mars. By presenting the results of a long series of resource-intensive experiments and our interpretation of the phenomena observed, we are hoping to elucidate some of the open questions surrounding the processes taking place in Mars’ cryptic region

Laboratory experiments
Measurements using unsorted dust
Measurements using fine dust
Observation of a Mars-like dust eruption in the laboratory
Temperature profiles of CO2 ice samples
Measurements using active pressure control
Conclusions
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