Asteroid densities
References:
    Britt, D. T.; Yeomans, D.; Housen, K.; Consolmagno, G.
    Asteroid Density, Porosity, and Structure
    in Asteroids III, W. F. Bottke Jr., A. Cellino, P. Paolicchi, and R. P. 
    Binzel (eds), University of Arizona Press, Tucson, p.485-500 (2002)
    File densbest.tbl obtained from http://www.psi.edu/pds/resource/density.html

    Behrend, R. and 48 others
    Four new binary minor planets: (854) Frostia, (1089) Tama, (1313) Berna,
    (4992) Debussy
    Astronomy & Astrophysics 446, 1177-1184 (2006)
    
    Marchis, F. and 17 others
    A low density of 0.8 g cm^-3 for the Trojan binary asteroid 617 Patroclus
    Nature 439, 565-567 (2006
     
    Asteroid      Dens +/-
     1 Ceres      2.12 0.04
     2 Pallas     2.71 0.11
     4 Vesta      3.44 0.12
    10 Hygiea     2.76 1.20
    11 Parthenope 2.72 0.12
    15 Eunomia    0.96 0.30
    16 Psyche     2.00 0.60
    20 Massalia   3.26 0.60
    22 Kalliope   2.50 0.30
    45 Eugenia    1.20 0.40
    87 Sylvia     1.62 0.30
    90 Antiope    1.30
   121 Hermione   1.96 0.34
   243 Ida        2.60 0.50
   253 Mathilde   1.30 0.20
   433 Eros       2.67 0.03
   704 Interamnia 4.40 2.10
   762 Pulcova    1.80 0.80
   804 Hispania   4.90 3.90
  1999 KW4        2.39 0.90
  2000 DP107      1.62 1.05
  2000 UG11       1.47 0.95
   854 Frostia    0.89 0.13
  1089 Tama       2.52 0.30
  1313 Berna      1.21 0.25
  4492 Debussy    0.90 0.10
   617 Patroclus  0.80 0.15