•Terrestrial
 Planets
 –Relatively small
 –Made primarily of rocky material:
 •Si,
 O, Fe, Mg  perhaps with Fe
 cores
  (Note
 – for earth H2O is only a very small fraction of the
 total)
 –
 •Jovian
 Planets
 –Relatively large
 –Atmospheres made of H2, He, with
 traces of CH4, NH3, H2O, ...
 –Surrounded by satellites covered with
 frozen H2O
 –
 •Within
 terrestrial planets inner ones tend to have higher densities
  (when
 corrected for compression due to gravity)
         Planet  Density  
 Uncompressed Density
    (gm/cm3)       
 (gm/cm3)
 – Mercury    
 5.44         
 5.30
 – Venus      5.24         
 3.96
 – Earth    
 5.50         
 4.07
 – Mars    
 3.94         
 3.73
 – (Moon)    
 3.36         
 3.40
 •