Laser-based exploration of underwater hydrothermal vents: a multi-sensor payload proof of concept
Pablo Sobron1, Laura M Barge
2, Anupam K Misra
3, Tayro Acosta-Maeda
4, Michael J Russell
2 and Ken Takai
5, (1)SETI Institute, Mountain View, CA, United States, (2)Jet Propulsion Laboratory, Pasadena, CA, United States, (3)University of Hawaii at Manoa, Hawaii Institute of Geophysics and Planetology, Honolulu, United States, (4)Hawai'i Institute of Geophysics and Planetology, Honolulu, HI, United States, (5)JAMSTEC Japan Agency for Marine-Earth Science and Technology, Kanagawa, Japan
Contact First Author: Pablo Sobron; psobron@seti.org
Previously Published Material: Partial results (<25%) were presented at the GeoRaman conference in 2014.
English Abstract:
Underwater hydrothermal systems (UHS) are produced by volcanic activity (e.g. black smokers) or directly by water-rock reactions (e.g. serpentinization and production of alkaline vents). Either way, commercially valuable seafloor metallic minerals precipitate from hydrothermal fluid as it interacts with the cooler ambient seawater at or beneath the seafloor, and a new industry is emerging: underwater mining. Since the hydrothermal fluids and mineral precipitates that form in a particular vent are highly specific to the geological setting, new instruments and adaptive exploration concepts that are conducive to analyzing a variety of vent conditions are needed in order to characterize seafloor mineral deposits. In response, we have developed an innovative concept for a robotic payload for UHS exploration. It utilizes high resolution 3D mapping and synergistic laser Raman and laser-induced breakdown spectroscopy (LRS+LIBS) to perform integrated, context-preserving, stand-off, in-situ characterizations of vent fluids and mineral precipitates.
In this work we describe an early-stage prototype and discuss a proof-of-concept demonstration of our payload. The samples are mineral precipitates from the chimney wall of a deep-sea black smoker at the mid-Okinawa Trough. We simulate underwater operation by immersing solid samples in a seawater tank and measuring LRS+LIBS from the outside of the tank. The microimages and the LRS and LIBS spectra show features consistent with sulfides, mainly chalcopyrite, a common metal sulfide mineral in acidic hydrothermal systems. The data obtained so far (1) demonstrate the feasibility of using LRS+LIBS for identifying minerals in black smoker precipitates in-situ and in near real time, and (2) help guide the definition of top-level instrument requirements, concepts of operation, and measurement strategies for the in-situ exploration of UHS in the deep-sea using laser-based robotic payloads.
