AAS 203rd Meeting, January 2004
Session 16 Asteroids, Planets and Planetary Satellites
Poster, Monday, January 5, 2004, 9:20am-6:30pm, Grand Hall

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[16.05] On the Origin of the Irregular Satellites

T. Grav, M.J. Holman (Harvard-Smithsonian Center for Astrophysics)

We present JHKs photometry of 10 Jovian and 4 Saturnian irregular satellites, taken with the Near-InfraRed Imager (NIRI) at the 8-m Gemini North Observatory on Mauna Kea, Hawaii. The observed objects have near-infrared colors consistent with C,F,D and P-type asteroids, although J~XII~Ananke and S~IX~Phoebe show weak indications of possible water features in the H filter. The four members of the Himalia-family have homogeneous near-infrared colors, as do the two members of the Gallic family, S~XX~Paaliaq and S~XXIX~Siarnaq, thus strengthening the arguments supporting the dynamical clusters as remainders of larger progenitors that were captured and subsequently broken up (Grav et al. 2003). Creating low resolution normalized reflectance spectra from 0.4 to 2.2 microns the irregular satellites are identified as C-type (J~VII~Pasiphae), F-type (J~VI~Himalia and S~IX~Phoebe), P-type (J~XII~Ananke and J~XVIII~Themisto) and D-type (J~IX~Carme and J~X~Sinope), showing significant diversity, and hinting to several different regions as the origin of the satellite progenitors.

The work was supported by NASA grant NAG5-13276 and by the Smithsonian Predoctoral Fellowship Program.

The author(s) of this abstract have provided an email address for comments about the abstract: tgrav@cfa.harvard.edu

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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.