This resistivity-temperature probe was deployed in the 270°C hydrothermal vent called 'Escargot' at the summit of Axial Volcano in 2013. Resistivity is an analoge for chlorinity or "saltiness' of the hydrothermal fluids. Boiling is common in these venting environments, governing gas concentrations, metal deposition, and perhaps life. A cabled version will be installed in 2014 providing real-time 24/7 data.
ROPOS dive #1618, VISIONS '13, Leg 3. Photo credit: NSF-OOI/UW/CSSF.