Diffuse Soil Degassing in Hydrothermal Areas of Mt. Melbourne, Antarctica: Insights for the Understanding of Cryovolcanism on Earth

Abstract

Cryovolcanism is a phenomenon reported in dwarf planets and satellites in the solar system and is characterized by the eruptions of volatiles under low-temperature conditions. However, there are clearly limitations to understanding it fully from observations far from Earth. From this point of view, Antarctica is one of the most extreme environments on Earth and is a very important region for modeling the extraterrestrial environment. Here, we report a maximum soil CO₂ flux value of 6120 g m^–2 d^–1 and a total CO₂ output of 8355 t d^–1 from the hydrothermal environment (up to 57.6 °C) of Mt. Melbourne, an active volcano located in Antarctica. In addition, fumarolic gases have δ¹³C values of −13.9 to −4.2‰ with CO₂ concentrations of 21.2–36.2 vol %. The corrected helium isotope ratios (Rc/Ra) of the gases are up to 2.21, indicating the magma degassing of Mt. Melbourne. However, hydrogen and oxygen isotopes of the ice samples inside the ice caves and ice towers in the hydrothermal region, similar to their surroundings, suggest that they are of largely atmospheric origin. Nevertheless, the circulated water caused hydrothermal alteration, producing minerals such as kaolinite and gibbsite, which greatly affected the moss habitat and microbial distribution of small greenhouse systems. Thus, the observations in this Antarctic hydrothermal system could potentially provide clues about extraterrestrial biological activity through cryovolcanism.