J/AJ/159/74 Disk-resolved photometric properties of Pluto (Protopapa+, 2020)
Disk-resolved photometric properties of Pluto and the coloring materials across
its surface.
Protopapa S., Olkin C.B., Grundy W.M., Li J.-Y., Verbiscer A.,
Cruikshank D.P., Gautier T., Quirico E., Cook J.C., Reuter D.,
Howett C.J.A., Stern A., Beyer R.A., Porter S., Young L.A., Weaver H.A.,
Ennico K., Dalle Ore C.M., Scipioni F., Singer K.
<Astron. J., 159, 74 (2020)>
=2020AJ....159...74P 2020AJ....159...74P
ADC_Keywords: Solar system; Photometry; Optical; Spectra, infrared
Keywords: Trans-Neptunian objects ; Pluto ; Radiative transfer simulations
Abstract:
A multiwavelength regionally dependent photometric analysis of Pluto's
anti-Charon-facing hemisphere using images collected by New Horizons'
Multispectral Visible Imaging Camera (MVIC) reveals large variations
in the absolute value and spectral slope of the single-scattering
albedo. Four regions of interest are analyzed: the dark equatorial
belt, Pluto's north pole, nitrogen-rich regions, and the mid-latitude
terrains. Regions dominated by volatile ices such as Lowell Regio and
Sputnik Planitia present single-scattering albedos of ∼0.98 at 492nm,
almost neutral across MVIC's visible wavelength range (400-910nm),
indicating limited contributions from tholin materials. Pluto's dark
equatorial regions, informally named Cthulhu and Krun Maculae, have
single-scattering albedos of ∼0.16 at 492nm and are the reddest
regions. Applying the Hapke radiative transfer model to combined MVIC
and Linear Etalon Imaging Spectral Array (LEISA) spectra (400-2500nm)
of Cthulhu Macula and Lowell Regio successfully reproduces the
spectral properties of these two regions of dramatically disparate
coloration, composition, and morphology. Since this model uses only a
single coloring agent, very similar to the Titan like tholin of
Khare+ (1984Icar...60..127K 1984Icar...60..127K), to account for all of Pluto's colors,
this result supports the Grundy+ (2016Sci...351.9189G 2016Sci...351.9189G) conclusion that
Pluto's coloration is the result of photochemical products mostly
produced in the atmosphere. Although cosmic rays and extreme
ultraviolet photons reach Pluto's surface where they can drive
chemical processing, observations of diverse surface colors do not
require different chemical products produced in different
environments. We report a correction scaling factor in the LEISA
radiometric calibration of 0.74±0.05.
Description:
We use Pluto data from the New Horizons Ralph instrument, which
consists of a visible multicolor/panchromatic mapper, the
Multispectral Visible Imaging Camera (MVIC), and a mapping IR
composition spectrometer, the Linear Etalon Imaging Spectral Array
(LEISA).
While observations of Pluto were acquired with MVIC from 2015 April
through July, we focus here on the five color images taken within the
last two days on approach to Pluto. See Table2 for more details.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 82 5 Multispectral Visible Imaging Camera (MVIC)
observations of Pluto
fig12c.dat 56 185 Combined New Horizons-MVIC and -LEISA mean
radiance factor (RADF) spectrum of
eastern Cthulhu (Data behind figure 12)
fig12lr.dat 56 185 Combined New Horizons-MVIC and -LEISA mean RADF
spectrum of Lowell Regio (Data behind figure 12)
fig13a.dat 29 19 Sample A Titan tholin optical constants
(Data behind figure 13)
fig13b.dat 29 19 Sample B Titan tholin optical constants
(Data behind figure 13)
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See also:
VI/155 : Topocentric positions of Pluto (Eglitis+, 2018)
J/A+AS/118/105 : Pluto 1991-1994 observations (Ryl'kov+, 1996)
J/A+A/375/285 : Photometric observations of Near-Earth Objects (Szabo+, 2001)
J/A+A/383/1054 : Astrometry of Pluto and Saturn in 1995-2001 (Rapaport+, 2002)
J/A+A/486/613 : Observation of Pluto (Veiga+, 2008)
J/A+A/515/A32 : Pluto, Charon, Nix, Hydra occultation 2008-15 (Assafin+, 2010)
J/A+A/551/A102 : Photometry of 16 Flora family asteroids (Kryszczynska, 2013)
J/A+A/553/A14 : Pluto's observations between 1997 and 2010 (Beauvalet+, 2013)
J/AJ/149/22 : Astrometry of Pluto from 1930-1951 observations (Buie+, 2015)
J/AJ/152/80 : Astrometry of Pluto & trans-Neptunian objects (Holman+, 2016)
J/AJ/158/196 : Near-Earth Object Survey (MANOS) spectro. (Devogele+, 2019)
J/ApJS/244/14 : Cassini CIRS observations of Titan 2004-2017 (Nixon+, 2019)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 27 A27 --- ObsID Request ID
29- 37 I9 --- MET [299104958/299178098] Mission elapsed time (1)
39- 63 A25 "datime" Date UTC mid-time of observation
65- 69 F5.2 km/pix Scale [0.6/21] Image scale
71- 76 F6.2 deg Long [161/197] Subsample-s/c longitude, East
78- 82 F5.2 deg Lat [25/43] Subsample-s/c latitude, North
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Note (1): The mission elapsed time (MET) is a counter on the spacecraft that
increments each second since launch and provides a unique timestamp
for the data.
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Byte-by-byte Description of file: fig12c.dat
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Bytes Format Units Label Explanations
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1- 18 F18.16 um lambda [0.49/2.4] Wavelength
20- 37 F18.16 --- RADFC [0.05/0.39] Radiance factor of eastern Cthulhu
39- 56 F18.16 --- e_RADFC [0.009/0.05] 1-σ error
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Byte-by-byte Description of file: fig12lr.dat
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Bytes Format Units Label Explanations
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1- 18 F18.16 um lambda [0.49/2.4] Wavelength
20- 37 F18.16 --- RADFL [0.04/0.77] Radiance factor of Lowell Regio
39- 56 F18.16 --- e_RADFL [0.01/0.08] 1-σ error
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Byte-by-byte Description of file: fig13a.dat
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Bytes Format Units Label Explanations
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1- 9 F9.7 um lambda [0.38/2.5] Wavelength
11- 19 F9.7 --- nA [1.6/1.8] The real part of the index of
refraction for sample A
21- 29 F9.7 --- kA [4.1e-4/0.1] The imaginary part of the index of
refraction for sample A
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Byte-by-byte Description of file: fig13b.dat
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Bytes Format Units Label Explanations
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1- 9 F9.7 um lambda [0.38/2.5] Wavelength
11- 19 F9.7 --- nB [1.6/1.8] The real part of the index of
refraction for sample B
21- 29 F9.7 --- kB [4.1e-4/0.1] The imaginary part of the index of
refraction for sample B
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 09-Mar-2020