DOI: 10.5061/dryad.xsj3tx9fd
title: Data from: Detecting sub-micron space weathering effects in lunar grains with synchrotron infrared nanospectroscopy

description: Space weathering processes induce changes to the physical, chemical, and
 optical properties of space-exposed soil grains. For the Moon, space
 weathering causes reddening, darkening, and diminished contrast in
 reflectance spectra over visible and near-infrared wavelengths. The
 physical and chemical changes responsible for these optical effects occur
 on scales below the diffraction limit of traditional far-field
 spectroscopic techniques. Recently developed super-resolution
 spectroscopic techniques provide an opportunity to understand better the
 optical effects of space weathering on the sub-micrometer length scale.
 This paper uses synchrotron infrared nanospectroscopy to examine
 depth-profile samples from two mature lunar soils in the mid-infrared,
 1500–700 cm-1 (6.7–14.3 µm). Our findings are broadly consistent with
 prior bulk observations and theoretical models of space weathered spectra
 of lunar materials. These results provide a direct spatial link between
 the physical/chemical changes in space-exposed grain surfaces and spectral
 changes of space-weathered bodies.
description: We used an iterative, non-linear, and robust peak fitting
 (deconvolution) procedure to determine peak parameters for SINS phase
 spectra. The procedure uses a trust-region minimization algorithm to fit a
 linear combination of Lorentzians with a local linear background to the
 data. Robustness is ensured by minimizing the residuals’ summed square and
 using bi-square weighting to reduce the impact of outliers. For more
 detail, see the Supporting Information for the associated
 publication.
description: <strong>Data Set S1.</strong> Raw SINS spectra for
 studied samples (sections 1–4 and the terrestrial anorthite standard). The
 relevant folders additionally contain the background spectral files (.CSV)
 that were used. These files are organized by section and scan.
 <strong>Data Set S2.</strong> This dataset is
 comprised of background-referenced and Fourier-transformed SINS spectra
 (.CSV). Note that both the amplitude and phase signals are included here.
 These files are organized by section and scan.
 <strong>Data Set S3.</strong> The compressed folder
 contains the initial conditions for the iterative fitting model as well as
 the peak parameters calculated thereby. These data are formatted as .CSV
 files. <strong>Data Set S4</strong>. The
 compressed folder contains 16 animated .GIF files (one for each linescan)
 displaying the fitted, un-renormalized phase spectra from each point in
 the linescan. The general darkening trend can be seen in spite of the
 noise. <strong>Data Set S5.</strong> The
 individual frames of the animations included in Data Set S4. Files are
 saved in .PNG format with a name in the style of:
 \S[Sample#]_LS[Scan #]_[Depth]nm_[Phase/Amp].png
 <strong>Data Set S6.</strong> This dataset contains
 the fitted spectra (.CSV) and 2σ confidence intervals (CI). The files
 contained in this dataset are formatted such that the first column
 contains the wavenumbers, the second column contains the fitted spectra
 evaluated at that wavenumber, and the third and fourth columns contain the
 CI for the fit.