Known as the "Res Probe," this novel seafloor instrument is designed to go inside the "throats" of high temperature (up to 480°C) black smoker chimneys to measure the resistivity and temperature of the hydrothermal vent fluids. Resistivity measurements, which serve as a proxy for chloride concentration, are an important component of hydrothermal fluid chemistry. Boiling is a common process beneath the seafloor at Axial, with boiling fluids observed issuing directly from vent orifices. Chloride measurements, therefore, are important to understand phase-separation processes, with implications for understanding metal deposition, gas generation, and microbial ecosystem development. Long-term measurements of hydrothermal fluids are difficult to obtain in such environments, as vent fluids at Axial Volcano typically have very low pH (~1.0).
The Res Probe was developed by Marv Lilley at the University of Washington. This cabled version of the Res Probe (TRHPHA301) was installed in 2014 at Escargot sulfide structure as part of the International District Hydrothermal Field (MJ03C) instrumentation.