So, what happened to the mass?
But, none of these appear to work very well.
- Dynamical excitation: Something excited the KB feeding most of mass inward.
- Collisional Grinding: In an excited KB collisions grind it down. (Stern & Colwell)
We can circumvent the mass depletion problem if:
The Nice Model supplies us a mechanism to doing this:
- we imagine the proto-disk was truncated near 30AU, and ....... (Levison & Morbidelli 2003)
- the Kuiper belt was pushed out.
- As Neptune scatters disk particles, they can be temporally trapped in resonances.
- The resonances are wider if Neptune's eccentricity is large.
- Recall that Neptune goes through a high eccentricity phase as it settles into its current orbit.
- So, the resonances start out wide and decrease with time.
- Objects can be trapped during this time.
- This process can capture the Kuiper belt that we see!
- 1 out of 1000 particles were trapped in the Kuiper belt.
- A 35 Earth-mass trans-Neptunian disk
0.04 Earth-mass in the Kuiper belt
- Thus, there is in good agreement with observed value.