Terrestrial Planet Formation and the Delivery of Water: Theory and Simulations Dara Zeehandelaar TERPS Conference, ASTR688 December 9, 2004 Dara Zeehandelaar TERPS Conference, ASTR688 December 9, 2004

1.Theory of Solar System formation 2.General Observations 3.Disagreement between theory and observations 4.Simulation 5.Results: -number of terrestrial planets formed -number of wet vs. dry terrestrial planets -number of terrestrial planets formed in the habitable zone OVERVIEW

General formation theory: the four-stage model 1. Initial condensation from the solar nebula atoms, molecules  grains 2.Early stage of accretion grains  km-sized planetesimals 3.Oligarchic growth, runaway accretion planetesimals  protoplanets 4.Late-stage dynamical evolution protoplanets  planets SOLAR SYSTEM FORMATION

Easy to explain with simple theory: - Terrestrial planets are close to the Sun - Jupiter exists A little bit harder: - Earth has liquid water Snow line believed to have been ~2 to 5 AU - Solar System has both wet and dry planets OBSERVATIONS

SOME MORE THEORY Late veneer theory: Terrestrial planets formed out of materials that originated at approximately their current distance from the Sun Hydration by cometary impacts D/H in oceans doesn’t match observed comets Migration theory: Planetesimals outside the snow line became eccentric Perturbed into crossing orbits with inner bodies Anhydrous material heated, H 2 O released as liquid

Jupiter’s mass: 0.03M J - 3 M J Jupiter’s semimajor axis: 4.0 AU AU Jupiter’s eccentricity: Formation time: Myr Density of solids: divide mass of region by total N, or fix planetesimal mass at 0.01M  Location of snow line: 2.0 AU AU SIMULATION INITIAL CONDITIONS ?

RESULTS 111 terrestrial planets (a.2M  ) formed in 44 simulations Mass (M  ) a (AU) eccentricity

RESULTS 111 terrestrial planets formed in 44 simulations 1 ocean = 1.5 x g = water in Earth’s hydrosphere

RESULTS 11 planets formed in the habitable zone: AU

CONCLUSION - current basic theory of Solar System formation is generally sound - problematic when tries to create terrestrial planets inside the snow line with liquid water - late veneer theory of hydration does not match observations - simple simulations, such as those by Raymond et. al., can create wet terrestrial planets in the habitable zone by late stage dynamical evolution, crossing orbits - future work: actually create the Solar System

REFERENCES Lissauer, J.J Annu. Rev. Astron. Astrophys. 31: Raymond, S.N., Quinn, T., Lunine, J.I Icarus 168: (October 28, 2004) ystem.jpghttp:// ystem.jpg (December 2, 2004)