Novel Chemometric Analysis Elucidates Elemental and Mineralogical Gradients within Hydrothermal Vent Precipitates using Laser-Induced Breakdown Spectroscopy (LIBS): An Investigation of Analytical Techniques to Facilitate the Search for Life on Ocean Worlds

Abstract:

Hydrothermal vents are dynamic, far from equilibrium environments that are capable of sustaining ecosystems with a rich biodiversity powered by geochemical redox gradients. They have a significant impact on ocean chemistry, may have been relevant for the origins of life on Earth, and are of interest as analog habitable environments for Ocean Worlds such as Enceladus and Europa. In situ studies of hydrothermal vents are needed to better understand how the formation, colonization, and geochemistry of these structures change over time and would be critical for any future life-detection missions to the oceans of Europa or Enceladus. However, such studies are rare and difficult to achieve because hydrothermal vents are typically found 1000s of meters beneath the ocean surface. One promising avenue is to conduct long-term in situ spectroscopic analysis with Laser-Induced Breakdown Spectroscopy (LIBS). LIBS is a robust, flight-ready technique that has been deployed on NASA’s Curiosity rover as a part of the ChemCam suite where it has spent the last 8 years characterizing the geochemistry of the Martian surface by generating over 700,000 spectra. Today LIBS remains a powerful tool for remote exploration and has been included onboard two new rovers heading to Mars, China’s Tianwen-1 and NASA’s Perseverance rover.

To determine the potential for LIBS to elucidate in situ elemental and mineralogical trends at hydrothermal vents, we used two flight-ready LIBS instruments, the ChemCam Engineering Qualification Model at Los Alamos National Laboratory and a novel LIBS system developed by Impossible Sensing. The samples studied were recovered from a chimney (Roane) within the Mothra Hydrothermal Field of the Juan de Fuca Ridge. Of particular interest was testing the feasibility of using novel chemometric techniques to tease out as much information about the samples as possible. In this regard, focus will be on the results of Multivariate Curve Resolution (MCR) to deconvolute which minerals are present. Notably, MCR is a powerful technique as it does not require prior knowledge about the sample. Lastly, we will briefly discuss ongoing work to deploy an underwater dive bot capable of carrying out long-term in situ LIBS at a hydrothermal vent on NSF’s Regional Cabled Observatory, which brings the global internet directly into the oceans.