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Evidence for Nitrogen-bearing Species on Umbriel: Sourced from a Subsurface Ocean, Undifferentiated Crust, or Impactors?

  • Authors: Richard J. Cartwright, David R. DeColibus, Julie C. Castillo-Rogez, Chloe B. Beddingfield, William M. Grundy, Tom A. Nordheim

Richard J. Cartwright et al 2023 The Planetary Science Journal 4 .

  • Provider: AAS Journals

Caption: Figure 3.

Grand average spectra (black) and 1σ uncertainties (light gray error bars) calculated using all individual spectra with band area and depth measurements >2σ for the 2.14 μm band (A, spectra b, c, f, g, i, l, m, and pin Figure 1), the 2.2 μm band (B, spectra b, c, e, f, h, i, j, l, and s in Figure 1), the 2.22 μm band (C, spectra a, d, g, i, j, m, n, and r in Figure 1), and the 2.24 μm band (D, spectra c, d, e, k, o, and q in Figure 1). All four grand average spectra are normalized to unity between 1.74 and 1.77 μm and offset vertically for clarity. The spectra have been smoothed using a 10–14 pixel wide boxcar function, whereas the 1σ uncertainties are shown at their native resolutions. The light purple zone highlights the wavelength range of the 2.14 μm band centers, the light blue zone shows the 2.2 μm band centers, the light green zone shows the 2.22 μm band centers, and the light red zone shows the range of 2.24 μm band centers (summarized in Figure 1 and the penultimate column of Tables A2, A3, A4, and A5, respectively). The dark gray line at the top of the plot is an atmospheric transmission model for Maunakea at zenith with 1.6 mm of precipitable water (50th percentile conditions), binned to simulate the spectral resolution of SpeX in SXD mode (R ∼ 750 at 2.2 μm, 0.″8 slit). This atmospheric spectrum demonstrates that Earth’s atmosphere is mostly transparent between 2.12 and 2.27 μm, with only a narrow CH4 gas feature overlapping the 2.2 μm band. Subpixel shifting routines used during data reduction help minimize residual telluric features. Thus, telluric contamination of the 2.2 μm band should be negligible.

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