Characteristic Features in the Spectra of Europa, Ganymede, and Callistoстатья
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Дата последнего поиска статьи во внешних источниках: 10 ноября 2014 г.
Аннотация:The results of groundbased spectrophotometry of the icy Galilean satellites of Jupiter—Europa,
Ganymede, and Callisto—are discussed. The observations were carried out in the 0.39–0.92 μm range with
the use of the CCD spectrometer mounted on the 1.25m telescope of the Crimean laboratory of the Stern
berg Astronomical Institute in March 2004. It is noted that the calculated reflectance spectra of the satellites
mainly agree with the analogous data of the earlier groundbased observations and investigations in the
Voyager and Galileo space missions. The present study was aimed at identifying new weak absorption bands
(with the relative intensity of ~3–5%) in the reflectance spectra of these bodies with laboratory measurements
(Landau et al., 1962; Ramaprasad et al., 1978; Burns, 1993; Busarev et al., 2008). It has been ascertained that
the spectra of all of the considered objects contain weak absorption bands of molecular oxygen adsorbed into
water ice, which is apparently caused by the radiative implantation of O+ ions into the surface material of the
satellites in the magnetosphere of Jupiter. At the same time, spectral features of iron of different valence (Fe2+
and Fe3+) values typical of hydrated silicates were detected on Ganymede and Callisto, while probable indi
cations of methane of presumably endogenous origin, adsorbed into water ice, were found on Europa. The
reflectance spectra of the icy Galilean satellites were compared to the reflectance spectra of the asteroids
51 Nemausa (Cclass) and 92 Undina (Xclass).