Remote-Raman spectroscopic study of minerals under supercritical CO2 relevant to Venus exploration

The authors have utilized a recently developed compact Raman spectrometer equipped with an 85 mm focal length (f/1.8) Nikon camera lens and a custom mini-ICCD detector at the University of Hawaii for measuring remote Raman spectra of minerals under supercritical CO2 (Venus chamber, ∼102 atm pressure and 423 K) excited with a pulsed 532 nm laser beam of 6 mJ/pulse and 10 Hz. These experiments demonstrate that by focusing a frequency-doubled 532 nm Nd:YAG pulsed laser beam with a 10× beam expander to a 1 mm spot on minerals located at 2 m inside a Venus chamber, it is possible to measure the remote Raman spectra of anhydrous sulfates, carbonates, and silicate minerals relevant to Venus exploration during daytime or nighttime with 10 s integration time. The remote Raman spectra of gypsum, anhydrite, barite, dolomite and siderite contain fingerprint Raman lines along with the Fermi resonance doublet of CO2. Raman spectra of gypsum revealed dehydration of the mineral with time under supercritical CO2 at 423 K. Fingerprint Raman lines of olivine, diopside, wollastonite and α-quartz can easily be identified in the spectra of these respective minerals under supercritical CO2. The results of the present study show that time-resolved remote Raman spectroscopy with a compact Raman spectrometer of moderate resolution equipped with a gated intensified CCD detector and low power laser source could be a potential tool for exploring Venus surface mineralogy both during daytime and nighttime from a lander.

Remote-Raman spectra of gypsum under supercritical CO2 (102 atm pressure and 423 K) as a function of time are measured, which show effect of simulated Venus atmosphere.Figure optionsDownload as PowerPoint slideResearch highlights
► We report remote-Raman spectra of minerals under simulated Venus atmosphere at 2 m distance.
► Raman spectra of sulfate, carbonate, and silicate minerals are measured.
► Time-resolved Raman could be a valuable tool for lander missions to Venus.