From Mars' Moons Formation to Submoons Hypothesis

Our study focuses on the formation and evolution scenarios of the Solar system small satellites, utilizing a N-body simulation code based on the Gauss-Radau integrator (Everhart (1985)) with a particular emphasis on collision detection. We started benchmarking our code by comparing our simulations with the results of Hyodo et al. (2022). In a second step we extended their work by adding physical effects to evaluate the likelihood of Bagheri et al. (2021) Phobos and Deimos formation scenario. In a third step, we used it to evaluate the possibility for moons of the Solar system to host their own moon.

Hyodo et al. (2022) argued that the formation of Mars’ moons based on a common progenitor fragmentation scenario as presented by Bagheri et al. (2021) was very unlikely. In fact, the former showed that under plausible assumption about the post-dislocation orbits of Phobos and Deimos based on the latter results, a collision between the two moons within 10 000 years is almost inevitable, leading to their annihilation. These outcomes were based on multiple N-body simulations considering Mars’ oblateness (J₂ and J₄ ) as well as mutual perturbations of point-masses moons. 
We extended these findings by including new factors such as Sun gravitational perturbations, Mars’ axial precession and nutation, and its triaxial shape (sectoral terms). Additionally, we revised some of Hyodo et al. (2022) initial conditions regarding the distribution of Phobos and Deimos post-dislocation. Our results indicate that these additional influences do not significantly alter the outcome; Phobos and Deimos still converge towards collision on a similar timescale, reinforcing the improbability of their formation via progenitor dislocation.

Furthermore, we have also used our integrator to assess the likelihood of subsatellite (moon of a moon) existence in the Solar system. By statistically analyzing collision and ejection probabilities of bodies orbiting some moons over extended periods, we identify potential candidates for discovering subsatellites. These findings provide valuable insights and targets for future observational efforts.

Figure 1: Cumulative fraction of collisions as a function of simulation time. The blue curve is a reproduction of Hyodo et al. (2022) result and the green curve represents the simulations with the additional effects mentioned above

 

 

References

  Amirhossein Bagheri et al. Dynamical evidence for phobos and deimos as remnants of a disrupted common progenitor. Nature Astronomy, 5(6):539–543, Jun 2021. ISSN 2397-3366. doi: 10.1038/s41550-021-01306-2.

 Edgar Everhart. An efficient integrator that uses gauss-radau spacings. International Astronomical Union Colloquium, 83:185–202, 1985. doi: 10.1017/S0252921100083913.

 Ryuki Hyodo et al. Challenges in forming phobos and deimos directly from a splitting of an ancestral single moon. The Planetary Science Journal, 3(8):204, 8 2022. doi: 10.3847/PSJ/ac88d2