Outbursts Upon Cooling of Low-Temperature Binary Mixtures: Experiments and Their Planetary Implications

TL;DR

This study investigates how certain binary mixtures undergo sudden outbursts upon cooling due to phase equilibrium effects, with implications for understanding geological processes on icy and rocky planetary bodies.

Contribution

The paper presents experimental evidence of freezing-induced outbursts in specific binary mixtures and discusses their potential planetary geological implications.

Findings

Outbursts observed in N2/CH4, CO/CH4, and N2/C2H6 systems.

Thermodynamic analysis explains the outburst mechanism.

Implications for icy moons and planetary geology.

Abstract

For many binary mixtures, the three-phase solid-liquid-vapor equilibrium curve has intermediate pressures that are higher than the pressure at the two pure triple points. This curve shape results in a negative slope in the high-temperature region near the triple point of the less volatile component. When freezing mixtures in the negative slope regime, fluid trapped below confined ice has latent heat released with more vapor upon cooling, and thus increases in pressure. If the rising pressure of the confined fluid overcomes the strength of the confining solid, which may be its own ice, it can produce an abrupt outburst of material and an increase in the system's overall pressure. Here, we report experimental results of freezing-induced outbursts occurring in the N2/CH4, CO/CH4, and N2/C2H6 systems, and provide insight into the phenomenon through a thermodynamics perspective. We also propose other binary systems that may experience outbursts and explore the geological implications for icy worlds like Titan, Triton, Pluto and Eris, as well as rocky bodies, specifically Earth and Mars.