P038-08
Investigation of Geothermal Silica Deposits Analog to Opaline Silica on Mars

Thursday, 10 December 2020: 07:21
Virtual
Shiv K Sharma1, Paul G Lucey2, Miles Egan3, Shuai Li4, Przemyslaw K Dera1 and Miles Egan, (1)University of Hawaii at Manoa, Hawaii Institute of Geophysics and Planetology, Honolulu, HI, United States, (2)Hawaii Inst Geophys & Planetol, Honolulu, HI, United States, (3)University of Hawaii, Hawaii Institute of Geophysics and Planetology,, Honolulu, HI, United States, (4)University of Hawaii at Manoa, Hawaii Institute of Geophysics and Planetology, Honolulu, United States
Abstract:
Geothermal brine deposits of opaline silica (SiO2.nH2O) have been used in the search of past life on Mars and early Earth because of its ability to capture and preserve biosignatures. In 2007 the Mars Spirit rover found opaline silica adjacent to 'Home Plate' in Gusev crater on Mars. Based upon comparison of thermal IR emission spectra, it has been suggested that terrestrial and Martian hydrothermal deposits of opaline silica originated from similar physical processes.

One of the Mars 2020 rover instruments, SuperCam, includes remote time-resolved (TR) Raman, laser-induced luminescence, LIBS and near-IR spectrometers that potentially could provide information about the nature of Martian silica deposits. In the present work, we have investigated opaline silica deposited from geothermal fluids from a geothermal well on the Island of Hawaii. We have used remote TR-Raman and luminescence spectroscopy in addition to x-ray diffraction and near-IR reflectance spectroscopy to characterize the opaline silica samples.

In the remote TR-Raman spectra of the silica sample excited with 532 nm pulsed laser, we found in addition amorphous silica bands, a band at 970 cm-1, corresponding to Si-OH stretching mode. The presence of the Si-OH bands indicates hydrous nature of the opaline silica samples. The near-IR spectra of opaline silica samples show bands corresponding to both OH and H2O molecules. The TR-luminescence spectra of the silica samples with 532 nm pulsed laser showed a very strong short-lived (<10 nano-sec) luminescence. The nature of the short-lived fluorescence implies presence of organic or biological material inside the opaline silica samples. The X-ray diffraction data confirmed the amorphous nature of the geothermal silica deposits. The bottom deposits over which the silica was formed, contained calcite, aragonite and halite minerals. The results of these investigations will be presented and discussed at the conference.

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