Bibcode
Lorenzi, V.; Pinilla-Alonso, Noemí; Emery, Joshua P.; Licandro, J.; Cruikshank, Dale P.; Grundy, Will; Binzel, Richard P.
Referencia bibliográfica
American Astronomical Society, DPS meeting #47, #210.08
Fecha de publicación:
11
2015
Número de citas
0
Número de citas referidas
0
Descripción
Continuous near-infrared spectroscopic observations during the last 30
years enabled the characterization of the Pluto's surface and the study
of its variability. Nevertheless, only few data are available in the
visible range, where the nature of the complex-organics can be
studied.For this reason, we started an observational campaign to obtain
the Pluto's relative reflectance in the visible range, with the aim of
characterizing the different components of its surface, and providing
ground based observations in support of the New Horizons mission. We
observed Pluto on six nights in 2014, with the imager/spectrograph
ACAM@WHT (La Palma, Spain). We obtained six spectra in the 0.40 –
0.93 µm range, that covered a whole Pluto's rotational period (6.4
days).To study longitudinal variations, we computed for all the spectra
the spectral slope, and the position and the depth of the methane ice
absorption bands. Also, to search for secular or seasonal variations we
compared our data with previously published results.All the spectra
present a red slope, indicating the presence of complex organics on
Pluto's surface, and show the methane ice absorption bands between 0.73
and 0.90 μm. We also report the detection of the CH4
absorption band at 0.62 μm, already detected in the spectra of
Makemake and Eris. The measurement of the band depth at 0.62 μm in
the new spectra of Pluto, and in the spectra of Makemake and Eris,
permits us to estimate the Lambert coefficient, not measured yet at this
wavelength, at a temperature of 30 K and 40 K.We find that all the
CH4 bands present a blue shift. This shift is minimum at the
Charon-facing hemisphere, where the CH4 is also more
abundant, indicating a higher degree of saturation of CH4 in
the CH4:N2 dilution at this hemisphere.Comparing
with data in the literature, we found that the longitudinal and secular
variations of the parameters measured in our spectra are in accordance
with previous results and with the distribution of the dark and bright
material as showed by the Pluto's albedo maps from New Horizons.In 2015,
new observations were run quasi-simultaneously with the New Horizons
flyby at 10 different Pluto longitudes (July 3 to 14) . The data are
currently being reduced.