Ida and Dactly

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Ida and Dactly

• Sam Williams
• http//www.cs.berkeley.edu/samw/249/

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243 Ida

• 56km x 24km x 21km
• 2.86AU (441M km from sun at flyby)
• Density 2.2 - 2.9g/cm3
• Mass 4x1016 kg
• Rotation 4.5hrs
• Albedo 0.24
• Some magnetic material

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Composition

• S-Type
• Silicates Nickle Iron
• Has some pyroxene, olivine, iron
• Thick Regolith (100m?)
• Abundance of iron minerals varies with location
  (blueish regions in false color)

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(No Transcript)
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Topography

• Heavily Cratered
• Many Degraded Craters
• 2Gyrs old (?)
• Cratered at formation?

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Dactyl

• 1.2 x 1.4 x 1.6km
• 90km from Ida
• (not well constrained)
• Craters from 80m to 300m
• Synchronous rotation
• Couldnt have survived
• for more than 100Myrs

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Dactyl(2)

• Similar, but not exactly the same composition
  (more pyroxene/olivine)
• Color doesnt correlate to any location on Ida
• Not a captured independent asteroid
• Probably not a fragment of Ida
• Probably captured about the same time as the
  creation of Ida (breakup of Koronis)

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Origins

• Break up of larger asteroid (lt300km) formed the
  Koronis group
• Koronis Family
• 2.82 - 2.95AU
• 1o inclination
• 6Myrs old ?
• (orbital dynamics)

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Other Asteroids with moons

• Main Belt
• 45 Eugenia
• 87 Sylvia
• 107 Camilla
• 121 Hermione
• 762 Pulcova
• 3671 Dionysus

• Trojan
• 617 Patroclus
• TNO/Plutiono
• (26308) 1998 SM165
• (47171) 1999 TC36