Tides and Elastic Bodies, the Dynamics of Moons and some Space Science and Geophysics
Developed for computer graphics, mass spring models are simple and fast and can be used to accurately track body deformations, and they accurately conserve angular momentum
but they have not previously been used in astrophysics.
We are creating a new field we call
`astro-elastodynamics' or 'soft astronomy'.
Our recent papers 1) proposing that tidal encounters
can cause crustal failure (and a new geophysical process!);
2) showing that we can accurately measure tidal spin down for spherical bodies
directly tying simulated rheology to tidal evolution;
3) measuring and understanding spin down rates of ellipsoids (and moving into an area
with no prior analytical predictions).
4) Explaining the high obliquity of Pluto and Charon's satellites
with a new type of spin resonance.
5) Studying propagation of impact excited seismic waves and normal mode excitation
on an asteroid.
For a talk on simulating tidal dynamics with mass-spring models see
Talk on tides! Spin dynamics and Cracking Charon!
I worked on the Uranian satellite system
to try and better understand the chaotic dynamics of closely packed orbiting systems.
It's the setting in the Solar system that is closest dynamically to the recently discovered
(from the Kepler mission) tightly packed compact planetary systems.
Brief forays into space science and geophysics are tagged below.
- A seismic study of asteroid Bennu using a Bennu shape model
and our mass/spring model:
Impact Excitation of a Seismic Pulse and Vibrational Normal Modes on Asteroid Bennu and Associated Slumping of Regolith
- Tilting Styx, Nix, Kerberos and Hydra;
Obliquity evolution of the minor satellites of Pluto and Charon ,
There are unidentified spin resonances in these simulations. Proposed
is a new spin-resonant mechanism for tilting the satellites.
- A new spin resonance model for the spin-secular/mean-motion resonance:
Tilting Styx and Nix but not Uranus with a Spin-Precession-Mean-motion resonance ,
- Tidal spin down and drift rates for triaxial ellipsoids like Haumea,
Tidal spin down rates of homogenous triaxial viscoelastic bodies ,
- We propose that rare past strong tidal encounters can account for formation
of chasmata and graben complexes on icy moons, Charon (and maybe even Mars). With
David, John and Cindy!
Crustal Failure in Icy
Moons and Satellites from a Strong Tidal Encounter ,
A movie on You-tube:
More elastic body movies at elastic movies
- Simulating tidal spin up and spin down with a mass spring model. With Julien!
The quality function k2/Q is
dependent on viscoelastic relaxation timescale! More importantly mass-spring model
can accurately simulate tidal evolution (and that means we can do many more things
with them ....).
Damped Mass-spring model Simulations of Tidal Spin down in a Kelvin-Voigt viscoelastic sphere ,
Movie: Click here:
Improved estimates of three-body resonance strengths and resonance overlap parameters
for Uranian moons in chains of mean motions resonances.
Resonant Chains and Three-body Resonances in the Closely-Packed Inner Uranian Satellite System ,