2008A&A...490..365P -
Astronomy and Astrophysics, volume 490, 365-375 (2008/10-4)
Surface characterization of Pluto and Charon by L and M band spectra.
PROTOPAPA S., BOEHNHARDT H., HERBST T.M., CRUIKSHANK D.P., GRUNDY W.M., MERLIN F. and OLKIN C.B.
Abstract (from CDS):
One of the main scientific objectives of NASA's New Horizons mission is to map the icy surface compositions of Pluto and its moon Charon. The encounter will be in 2015. Meanwhile remote observations from earth and space are the most suitable means to enhance further our knowledge of the Pluto/Charon system. We intend to assist the New Horizons mission by improving our knowledge of Pluto's and Charon's surface compositions. Specifically, we extend the wavelength coverage of the surface spectroscopy beyond the K band, with the goal to detect further surface ice absorption bands predicted from the models that are based on the available JHK spectra, and to search for signatures of yet unknown ices. In particular we aim to resolve the binary system Pluto/Charon and to obtain, for the first time, spectra up to 5µm of the two objects resolved.Spectroscopic measurements of Pluto/Charon taken with the adaptive optics instrument NACO at the ESO VLT in the interval 3-7 August 2005 were obtained. The nature and properties of the compounds present on the surface of Pluto and Charon are investigated by applying a Hapke radiative transfer model to the measured spectra.We present Pluto's reflectance spectrum in the wavelength range (1-5)µm. Apart from known and expected absorption bands of methane ice, our Pluto spectrum reveals a new absorption band centered near 4.6µm, not previously detected. This absorption band could be related to the presence of CO and nitriles (compounds of C and N connected with a triple bond). A geographic mixture of pure methane ice with two different grain sizes, methane and CO ice diluted in nitrogen, CH2CHCN and titan tholin gives the best fit to Pluto's spectrum, although not in all details. Differences compared to published Pluto spectra from 2001 taken at similar longitude could be due to a different surface coverage in latitude or to a possible resurfacing process on Pluto. Charon's spectrum is measured in the wavelength range (1-4)µm. The surface of Charon can be modeled by pure water ice darkened by a spectrally neutral continuum absorber.
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Syntax of coordinates is : "ra dec (wtype) [error ellipse] quality bibcode" :
ra dec : right ascension and declination (unit and frame defined according to your Output Options)
Grey values are increasing the original precision due to the computation of frame transformations
(wtype) : wavelength class for the origin of the coordinates (Rad, mm, IR, Optical, UV, Xray, Gam)
[error ellipse] : measurement uncertainty, on (ra,dec) if the positional angle is 90 degrees, on (majaxis,minaxis) otherwise (in mas at defined epoch in the original catalogue),
position angle (in degrees North celestial pole to East)
Syntax of coordinates is : "ra dec (wtype) [error ellipse] quality bibcode" :
ra dec : right ascension and declination (unit and frame defined according to your Output Options)
Grey values are increasing the original precision due to the computation of frame transformations
(wtype) : wavelength class for the origin of the coordinates (Rad, mm, IR, Optical, UV, Xray, Gam)
[error ellipse] : measurement uncertainty, on (ra,dec) if the positional angle is 90 degrees, on (majaxis,minaxis) otherwise (in mas at defined epoch in the original catalogue),
position angle (in degrees North celestial pole to East)
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References (4 between 1850 and 2024) (Total 4)
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