The Grand Tack Hypothesis

Transcription

1 The Grand Tack Hypothesis A low mass for Mars from Jupiter s early gas-driven migration Walsh et al. 2011, Nature, 475, 206 Alexia Lewis & Giada Arney ASTR557 02/02/2012

2 Outline Planetary migration The Grand Tack model Why is this a good model? Limitations Summary

3 Planetary Migration Type I Migration Fast inward migration due to gravitational interactions with the gaseous component of the proto-planetary disk Movie credit:

4 Planetary Migration Type II Migration Massive planet opens gap in disk Accretion continues from gas that overflows gap edges Exchange of angular momentum locks planet to disk, slower inward migration occurs

5 Planetary Migration Type III Migration Runaway migration

6 The Grand Tack Model

7 Initial Conditions Planets Jupiter M = MJ a0 = 3.5 AU Type II migration Migrates inward for 105 yrs Uranus M = 5 Mearth a0 = 6 AU No migration Saturn M = 30 Mearth a0 = 4.5 AU Type I migration at 60 Mearth at ~105 yrs Neptune M = 5 Mearth a0 = 8 AU No migration

8 Initial Conditions Planetesimals S Type M = 3.7 M earth 0.3 AU< a 0 < 3.0 AU Inner Disk C Type M = 15 M earth 3.5 AU < a 0 < 13 AU Inter-planetary and trans- Neptunian objects Planetary migration pushes S-type objects inward Mass of disk < 1 AU reaches 2 M earth 14% of inner disk scattered outwards

9 S-type C-type C-type Eccentricity Semimajor axis (AU)

10 The Grand Tack Saturn and Jupiter locked in 2:3 resonance at 1.5 AU Interactions between planets and disk occur at Jupiter s inner Lindblad and Saturn s outer Lindblad resonances The torques at these resonances are Get outward migration when Jupiter s inner torque dominates

11 Credit: Frederic Masset

12 The end of the model Jupiter and Saturn migrate outwards in resonance Catch Uranus and Neptune in resonance 600 kyrs for planets to finish migrating and obtain full masses

13 Asteroids Planets scatter material back into asteroid belt region as they migrate outwards 0.5% of S-type material 0.5% of material from Jupiter-Neptune region (C-type) 0.025% of trans-neptunian (C-type Asteroid belt population in place at end of planet migration

14 S-type C-type C-type

15 Why is this a good model? Mass of Mars Distribution of asteroids Sources of water for Earth Nice Model Initial conditions

16 Terrestrial Planet Formation Truncated inner disk for terrestrial planet formation Hansen 2009: The degree to which a true physical model can realize these conditions is unclear

17 Mass of Mars Inner disk truncated at 1 AU Build-up of planetary embryos at 1 AU S-type C-type C-type

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19 The Asteroid Belt The anhydrous S-Type asteroids originate in the inner disk, and the primitive C- Type are from the outer disk The inner belt is dominated by S-Types (ordinary chondrites) and the outer belt by C-Types (carbonaceous chondrites) Difficult to explain differences between carbonaceous and ordinary chondrites if they formed in the same location

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21 S-type C-type C-type

22 Source of Water Simulations show C-type asteroids on orbits crossing the forming terrestrial planets (3-11) x 10-2 M earth of C-type material is delivered to the terrestrial planet region This is 6-22x the minimum mass required to bring the current amount of water to Earth

23 Output Initial Conditions Four outer planets in compact resonant configuration approximate assumption made by Nice model at disappearance of gas The main weakness of the Nice model is that the initial conditions of the planets were chosen without concern for the previous phase of planetary evolution when the protoplanetary gas disk was still in existence. Morbidelli et al Nice reproduces outer Solar System, Grand Tack reproduces inner Solar System

24 Limitations Accretion of giant planets not well understood Pierens & Raymond 2011

25 Summary The Grand Tack is a model that explains the architecture of the inner Solar System. It reproduces Distribution of asteroids Small mass of Mars compared to Earth and Venus Together with the Nice Model, it gives us a better understanding of the formation of our Solar System.