Water

• It has long been thought that embryos at 1AU were dry.
• Water came from near or beyond the snow-line.
• Convenient to divide this into three sources:
  1. Comets (~%50 ice) during Oort cloud formation. (Levison et al. 2001)
  2. Asteroids (Carbonaceous chondrites contain ~ 10% water).
     . Most of our systems have big gaps between terrestrial and giant planets asteroid belts.
  3. Planetary embryo(s) from asteroid belt (Morbidelli et al. 2000).
     • Not all terrestrial planets are wet due to small number statistics.
       XXXX May explain Venus.

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Extremes from our systems: (preliminary results)

• This system is dry.
  Outer regions cleared before terrestrial planets form.
• The blue planet is very wet.
  
  • Indeed, this planet accreted 10 Oceans of water from comets alone! Habitable?