1. UNESP, São Paulo State University , Grupo de Dinâmica Orbital e Planetologia, Guaratinguetá, CEP 12516-410, SP, Brazil
2. Department of Earth, Environmental and Planetary Sciences , 6100 Main MS 126, Rice University, Houston, TX 77005, USA
3. Department of Physics and Astronomy , 6100 Main MS-550, Rice University, Houston, TX 77005, USA
4. Max-Planck-Institut für Astronomie , Königstuhl 17, D-69117 Heidelberg, Germany