Surface Enhanced Raman Spectroscopy of Planetary Materials Using Laser Deposited Plasmonic Gold Nanoparticles

Abstract

Detection of trace materials on planetary surfaces and changes to the surface composition or structural modifications is important for identifying contaminants and other near-surface changes that may contain valuable geological information. This work demonstrates a surface-enhanced raman spectroscopy (SERS) approach based on laser deposition of Au plasmonic nanoparticles onto several relevant mineral surfaces. A pulsed 1064 nm wavelength laser is used to ablate a thin gold film and deposit Au nanoparticles directly onto selected regions of an olivine mineral sample as the substrate, enabling localized in situ SERS probing. Thin surface layers of four examples of relevant planetary simulants, such as CSM-LHT, JSC-RN, OPRH4-W30, and NU-LHT-4M, which identify as lunar highland and Martian soil analogs, were deposited on olivine substrate to emulate surface-level deposits. After nanoparticle deposition on simulants, Raman features associated with these plagioclase-rich simulants became significantly more distinct, whereas conventional Raman measurements of the same thin layers produced only weak or incomplete signatures. The technique was also shown to detect a mixed surface layer containing JSC-RN simulant and TiO2 (anatase), demonstrating sensitivity to multiphase systems. The results indicate that laser-deposited plasmonic nanoparticles can enhance Raman detection of thin surface materials on rough mineral substrates with an effective enhancement on the order of ∼104, offering a promising route for in situ planetary material analysis. This work demonstrates a path for in situ identification using SERS of planetary minerals with suppressed Raman signatures from space weather exposure. These results will advance planetary surface analysis by enabling localized in situ detection of thin surface deposits, alteration layers, and mixed mineral phases on rough substrates, with relevance to lunar and Martian exploration, astrobiology, geological sensing, and future instrument development for trace material detection in challenging environments. The same approach is relevant to geological surface analysis on Earth, where thin alteration layers, mineral coatings, and fragile surface deposits can be difficult to probe using conventional Raman methods, and the demonstrated method would be suitable for analyzing a variety of solid surfaces.