Terrestrial Planet Formation and the Delivery of Water: Theory and Simulations

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Terrestrial Planet Formation and the Delivery of
Water Theory and Simulations

• Dara Zeehandelaar
• TERPS Conference, ASTR688
• December 9, 2004

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OVERVIEW

• Theory of Solar System formation
• General Observations
• Disagreement between theory and observations
• Simulation
• Results
• number of terrestrial planets formed
• number of wet vs. dry terrestrial planets
• number of terrestrial planets formed in the
  habitable zone

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SOLAR SYSTEM FORMATION

• General formation theory the four-stage model
• 1. Initial condensation from the solar nebula
• atoms, molecules ? grains
• Early stage of accretion
• grains ? km-sized planetesimals
• Oligarchic growth, runaway accretion
• planetesimals ? protoplanets
• Late-stage dynamical evolution
• protoplanets ? planets

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OBSERVATIONS
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
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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 doesnt match
observed comets Migration theory Planetesimals
outside the snow line became eccentric Perturbed
into crossing orbits with inner bodies Anhydrous
material heated, H2O released as liquid
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SIMULATION INITIAL CONDITIONS
Jupiters mass 0.03MJ - 3 MJ Jupiters semimajor
axis 4.0 AU - 7.0 AU Jupiters eccentricity 0.0
- 0.2 Formation time 0 - 10 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 - 5.0 AU
?
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RESULTS
111 terrestrial planets (a lt 2 AU, M gt .2M?)
formed in 44 simulations
a (AU)
Mass (M?)
eccentricity
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RESULTS
111 terrestrial planets formed in 44 simulations
1 ocean 1.5 x 1024 g water in Earths
hydrosphere
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RESULTS
11 planets formed in the habitable zone 0.8 -
1.5 AU
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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

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REFERENCES
Lissauer, J.J. 1993. Annu. Rev. Astron.
Astrophys. 31129-74 Raymond, S.N., Quinn, T.,
Lunine, J.I. 2004. Icarus 1681-17 http//exoplane
ts.org/almanacframe.html (October 28,
2004) http//www.manitobamuseum.ca/images/Our20So
lar20System.jpg (December 2, 2004)