Tag: ta2.5

22-EPN3-043: Investigating Reflectance and Emissivity Spectra of Minerals and Analogs under Vacuum to Support Analyses of Lunar Spectra

Visit by Janice Bishop of the SETI Institute (USA) and Kierra Wilk of Brown University (USA) to TA2 Facility 5 – DLR Planetary Spectroscopy Laboratory (Germany).
Dates of visit: 12-21 November 2023

Report Summary: Laboratory experiments were conducted to investigate H₂O and OH species in minerals under different environmental conditions in order to improve our understanding of hydrated
species (H₂O/OH) identified on the Moon through both the H₂O stretching bands near 3 μm and the H₂O bending vibrations near 6 μm.

We were able to run reflectance and emission spectra under vacuum and different temperatures at the DLR Planetary Spectroscopy Laboratory (PSL) for several lunar analogues, plus a couple of sulfate analogues for Mars and an ammonia clay analog for Ceres. Measuring both the 3 μm and 6 μm spectral features with the same instrument under the same conditions was very helpful for our lunar project because these have been characterised using different instruments under different conditions at the Moon.

The hydration features near 2.7-3 μm are observed in the Moon Mineralogy Mapper (M3) hyperspectral imaging data on board the Chandrayaan-1 orbiter and exhibit variations near 2.7 and 2.9 μm that could be consistent with changes in hydroxyl (OH) and molecular H2O species in the lunar regolith. The band observed near 6 μm in telescopic spectra of the Moon are only due to H₂O species and not to OH. We observed changes with increasing vacuum level and increasing temperature for both features at 3 and 6 μm for our lunar samples. We also observed changes in the Mars and Ceres analogs under vacuum and after heating. Obtaining these spectral measurements at the DLR-PSL provided essential data for our planetary science projects.

20-EPN2-021: Construction of lunar mineral maps using NIR hyperspectral data in combination with GRS and/or LIBS data

Visit by Kyeong Ja Kim of the Korea Institute of Geoscience and Mineral Resources (Korea) to TA2 Facility 5 – DLR Planetary Spectroscopy Laboratory (Germany).
Dates of visit: 16-27 October 2023

Report Summary: There were three objectives of the project:

1. Development of a Bayesian method for spectral unmixing of NIR hyperspectral image data acquired by the Moon Mineralogy Mapper (M³) instrument with Gamma Ray Spectrometer (GRS) and Laser Induced Breakdown Spectroscopy (LIBS) data
2. Construction of global and regional maps of the main minerals of the Moon which are constrained by the elemental abundances measured by GRS and/or LIBS
3. Ingestion of the obtained map product into a mobile Geographic Information System (GIS).

Objective (1) was investigated with spectral analysis of various terrestrial analog samples along with lunar simulants to characterise image data that respond to mineralogical features which are directly connected to the mineralogical features of the moon investigated by remote sensing spectral data, especially M³ by Chandrayaan-1. The data obtained at DLR will be characterised with M³ data to understand mineralogical features as well as data obtained from KPLO GRS (KGRS). This approach will
guide in understanding regional mineralogical identification and elemental information that guides in investigation of lunar geology and resource prospecting. Objective (2) has been investigated using global elemental maps derived from M3 and Lunar Prospector GRS data.

The mineral maps constructed so far can be updated once KGRS data become available. Objective (3) will be addressed shortly by importing the constructed mineral maps into the K-Mapper software running on mobile devices. This will be invaluable for future human missions and the lunar resources prospecting international campaign as part of the Artemis 3+ activities.

20-EPN-004: Spectroscopy of Shock Processed Planetary Analogues Mimicking Impact Events on the Surface of Mercury

Visit by Arijit Roy and Wafikul Khan of the Physical Research Laboratory, Ahmedabad (India) to TA2 Facility 5 – DLR Planetary Spectroscopy Laboratory (Germany).
Dates of visit: 09-13 October 2023

Report Summary: The surface of the airless Solar System bodies has been modified both physically as well as chemically by the impacts induced shock processing. Planetary scientist uses multispectral
remote sensing technique to understand the surface chemistry of these airless planetary bodies. Different spectral ranges reveal distinct descriptions and characteristics of the observed planetary surface. Like, VIS-IR spectroscopy focused on a rocky planet provides insights into the distribution of iron (Fe) and titanium (Ti)-rich minerals, spanning both its igneous and sedimentary phases. In contrast, IR spectroscopy exposes the abundance of silicon-oxygen (Si-O) bonds, offering a glimpse into the bulk mineralogy of the surface. This leaded to the better understanding of the abundance of minerals and their distribution on the different planetary surfaces. Olivine is often observed on the surface of different Solar System objects such as Venus, Mercury, Our Moon, and Asteroid Vesta. In the case of Mercury
impacts allowed olivine to mixed with other abundant sulphides molecules and further processed by shock wave which induced a physico chemical changes leaded to a change in the spectral signature of the Mercury surface.

To address this issue we studied shock processing (5.6 M) of the olivine (dunite) with sulphur, where the mixture was processed at a temperature ~ 7300 K, for 2ms. The shock processed samples later analysed using PSL, DLR’s bi directional reflection spectroscopy set up from UV to FIR wavelength range.Results from this work will help the planetary science community to build a spectral library for the future planetary missions.

22-EPN3-046: Integrated Spectroscopic Study of Apollo 16 Sample and Anorthositic Lunar Meteorite

Visit by Prateek Tripathi, Indian Institute of Technology, Roorkee (India) to TA2 Facility 5 – DLR Planetary Spectroscopy Laboratory (Germany).
Dates of visit: 10-17 December 2023

Report Summary: The objective was to characterise 15 lunar minerals, the Apollo 16 sample, and the Tissertiline lunar meteorite using integrated spectroscopy with the Bruker Vertex80V FTIR instruments at the Planetary Spectroscopy Laboratory (PSL). The minerals studied included pigeonite, augite, ilmenite, orthopyroxenes, olivine, anorthite, and bytownite, with grain sizes ranging from 25-125 μm. Additionally, Apollo 16 sample 62231.44, collected from the rim of Buster Crater and highly mature, was included in the analysis. The methodologies employed integrated bidirectional reflectance spectroscopy in the visible (VIS) and near-infrared (NIR) ranges at 30° and 45° angles, separate hemispherical measurements in VIS and NIR, and emission spectroscopy at temperatures of 70°C, 100°C, and 130°C over the mid-infrared range. The spectral range covered was 0.2 – 150 μm, with a resolution ranging from 0.1 – 8 cm⁻¹. In total, 204 spectra were acquired in ten days of visit, including standards (endmembers/lunar minerals), the Apollo 16 sample, the lunar meteorite, and a black body.

Bidirectional measurements yielded 102 spectra (VIS and NIR separately), hemispherical measurements provided separate VIS and NIR spectra totaling 51, and emissivity measurements contributed 51 thermal emission spectra. This comprehensive methodology allowed for the observation of the effects of temperature and grain size on spectral properties. This integrated optical through thermal spectroscopy approach successfully characterises lunar sample and results in a spectral library that will aid in the interpretation of future lunar mission data for composition identification and resource potential
assessment.

22-EPN3-068: Vacuum Heating Effects on Spectroscopic Properties of Carbonaceous Chondrite Meteorites

Visit by Edward Cloutis and Cain Kiddell, University of Winnipeg (Canada), to TA2 Facility 5 – DLR Planetary Spectroscopy Laboratory (Germany).
Dates of visit: 10-17 December 2023

Report Summary: This project was designed to investigate how conditions that may have affected dark carbonaceous asteroids affect our ability to detect and characterise them. We specifically investigated how exposure of carbonaceous meteorites (which are presumed to derive from carbonaceous asteroids) to the vacuum of space, as well as to heating, affect their spectral reflectance properties. Heating of carbonaceous asteroids may occur during their accretion and decay of radioactive elements, or from close passes to the Sun. We studied a number of different classes of carbonaceous meteorites of low petrologic grade, and will compare them to similar meteorites that show evidence of heating.

We found that vacuum exposure has its greatest effect on the depth and shape of the 3 micron-region water absorption band, while the 2.7 micron region absorption feature, associated with hydroxyl (OH) was largely unaffected.Heating led to a number of spectral changes which we continue to investigate, however preliminary results indicate that heating can affect absorption bands associated with iron. We have also found that the changes in spectral reflectance properties are a function of heating temperature. This results should enable us to constrain the temperatures to which carbonaceous asteroids have been exposed, and provide insights into conditions that prevailed in the early Solar System.

20-EPN2-075: Emissivity Measurements of Proposed Source Minerals for Venus Anomalous Regions

Visit by Erika Kohler, NASA Goddard Space Flight Centre (UK), to TA2 Facility 5 – DLR Planetary Spectroscopy Laboratory (Germany).
Dates of visit: 1-15 December 2022

Report Summary: This study directly measured the emissivities of four Venus-mineral analogues at Venus relevant temperatures and reflectivity spectra pre- and post- heating. Mission and ground-based observations of Venus show several anomalous regions related to elevation, but the variations are unknown to be compositional or morphological in nature. The comparison of emissivity measurements from candidate minerals at Venus surface conditions and reflectivity measurements will demonstrate whether mineralogical composition can be identified in future Venus missions and will constrain the source of the Venus highland radar anomalies. The results of this study will maximise the return of previous and future Venus missions that take surface measurements by contributing to the database of Venus analogues being compiled at the Planetary Spectroscopy Laboratory.

20-EPN2-100: Spectroscopic Identification of Experimental Basalt Alteration Products Under Venus Conditions

Visit by Molly McCanta, University of Tennessee (USA), to TA2 Facility 5 – DLR Planetary Spectroscopy Laboratory (Germany).
Dates of visit: 14 – 20 October 2022

Report Summary: Experiments and thermodynamic modelling clearly show that sulfates are a common alteration product under the high temperature, CO₂-SO₂-rich conditions at the surface of Venus. The exact sulfates present depend on the original basalt composition, with anhydrite (CaSO₄) and thernardite (Na₂SO₄) having been observed in the lab (Reid et al., 2023).

Alteration rates calculated from these experiments suggest that sulfate coatings may develop geologically fast and therefore alteration coatings may obscure the original protolith. Additionally, the spectral features of these high temperature sulfates are not well constrained. Although many critical sulfate minerals are stable to temperatures > 500C, previous analytical data has generally explored sulfate-temperature spectral relations to ~100C. The surface of Venus is significantly hotter at 470C. Thus is makes sense to investigate both the effects of variable thickness sulfate coatings and the spectral properties of sulfates under Venus surface conditions to gain a better understanding of their behaviour.

The next set of Venus missions will have observational capabilities in the thermal emission spectrum (range) and high T sulfate spectra are presented in another paper (Dyar ref); here we present data for the effects of high T on visible near-infrared (VNIR) sulfate spectra. In addition, we have conducted experiments to determine the effects of sulfate coating thickness on the underlying surface spectra. The data presented may help determine future mission capabilities to both recognise and analyse sulfate-bearing materials under high T conditions as well as constrain the original, unaltered surface composition.

20-EPN2-048: Heating effects on the spectral reflectance properties of carbonaceous chondrite meteorites

Visit by Edward Cloutis, University of Winnipeg (Canada), to TA2 Facility 5 – DLR Planetary Spectroscopy Laboratory (Germany).
Dates of visit: 28 August – 2 September 2022

Report Summary: Carbonaceous chondrites are likely derived from dark (C-class) asteroids. Sample return missions to dark asteroids (JAXA Hayabusa-2, OSIRIS-REx) will allow us to link specific meteorites to these possible parent bodies. The compositions of the sample return target asteroids (Ryugu and Bennu) are currently unknown, as are the compositions of other dark asteroids. Dark asteroids are important scientific targets because they may have delivered prebiotic organic molecules to the early Earth.To help address how we can determine the compositions of dark asteroids, particularly whether they are primitive, aqueously-altered, and/or heated, we conducted a series of experiments at PSL designed to address this.

Specifically, we performed heating experiments, in vacuum, on clay minerals present in carbonaceous chondrite meteorites, and measured their subsequent spectral reflectance properties, as well as on samples heated in previous experiments (clays, carbonaceous chondrites, carbonaceous chondrite analogues), focusing on the most diagnostic spectral feature relevant to dark asteroids – the 3 micron region hydroxyl/water absorption band. The results are still being analysed, but it appears that heating in vacuum and exposure to vacuum cause changes in the depth and shape of this absorption feature, as well as the albedo, spectral slope, and appearance of additional absorption features. The results of this study will provide important constraints into the composition and history of dark asteroids.