UV laser‐induced fluorescence spectroscopy as a non‐destructive technique for mineral and organic detection in carbonaceous chondrites

Abstract

Here, we discuss the merits of non-destructive UV laser-induced fluorescence spectroscopy (LIF) as a flight or laboratory instrument to analyze organic and mineral material in samples on or returned from carbon-rich asteroids such as (101955) Bennu by NASA's OSIRIS-REx mission. LIF is a unique instrument that is non-destructive while acquiring data, and allows for no sample preparation, crushing, or cutting. This method provides spectral data indicative of specific minerals and organics in less time than Raman spectroscopy, and can be set up to produce 2-D raster images of areas of interest. Furthermore, if an LIF system is set up with a gated CCD camera, time-resolved fluorescence spectroscopy can be performed, providing a unique identification tool for organic and mineral contents using fluorescence decay over several nanoseconds. This technique was used to analyze millimeter-sized chondrules and calcium-aluminum-rich inclusions on four carbonaceous chondrite samples provided by the Royal Ontario Museum: Murchison (CM2), Allende (CV3), NWA 11554 (CV3), and NWA 12796 (CK3). The LIF 2-D maps, point spectra, and time-resolved fluorescence data and mineral identifications using LIF were compared to that of well-known techniques such as Raman spectroscopy and SEM/EDS.

Combined Spectroscopic Analysis of Terrestrial Analogs from a Simulated Astronaut Mission Using the Laser-Induced Breakdown Spectroscopy (LIBS) Raman Sensor: Implications for Mars

“…Furthermore, we show that LIF is a useful technique for preliminary ''triage'' analyses of any type mineral or organic, which should then be followed by more detailed analyses (likely Raman and Infrared spectroscopies) or destructive analyses (LIBS). 71,72 Typical acquisition parameters of the LIRS instruments for LIF and UV Raman are detailed on Cote et al, 35 where LIF mode generates the quickest measurements, and as such, has been identified as a useful technique for pre-screening targets for further analysis.…”

“…However, these interpretations have to be taken with care given the sensitivity of the results to the organic versus minerals variability in the samples. In this regard, Lymer et al 71,72 showed the necessity to create libraries of different substrates and organics to improve such featured capabilities. Given the fast speed and high sensitivity in the detection of organic structures, LIF is an important complementary method for organic detection.…”

Organic Material Distribution in Mars-Analog Volcanic Rocks, as Determined with Ultraviolet Laser-Induced Fluorescence Spectroscopy

“…The instrument setup described in the works of Eshelman (2016) and Lymer (2017) was modified for use during this study (Fig. 2).…”

“…A key objective of this study was to examine the spatial distribution of organic material in the basalt samples. To that end, raster maps of a sample surface were created by combining stage movement and spectral measurements in an automated program [as in Lymer (2017)]. For this study, a 1 cm 2 area was chosen on each slide for analysis.…”

“…The angle of rotation was recorded. The stage would move stepwise by the distance indicated in the automation program (0.25 mm/step), and the Andor iStar would take a LIF measurement at each step [see Lymer (2017)]. As the step size was smaller than the laser spot size, each discrete measurement window (laser spot size) would overlap spatially with the next.…”