Origin of Phobos and Deimos : Plausibility of a Fragmentation Scenario

The origin of Phobos and Deimos remains uncertain. Over the years, several hypotheses have emerged: an impact between Mars and a planetesimal (Craddock (2011)), accretion from a debris disc ( Hesselbrock and Minton (2017)) or an asteroid capture (Hunten (1979), Rosenblatt (2011)). In 2021, Bagheri et al. (2021) proposed that both moons are fragments of a larger progenitor. Indeed, based on tidal forces, the authors have integrated backwards the orbital elements of the two satellites from their current positions, showing that the orbits of the two satellites may have crossed in the past. This leads them to conclude on a common origin. Hyodo et al. (2022)) then showed, in a simplified dynamic framework, that the post-fragmentation orbital elements resulting from this integration do not allow the newly-formed fragments to survive to the present day. In fact, a destructive collision between the two fragments seems difficult to avoid within 10,000 years of their formation. Thanks to a large number of N-body simulations, we have extended these results with a more complex physical model. We confirm the results of Hyodo et al. (2022) by taking into account more realistic physics: the survival of Phobos and Deimos until the present day in the formation scenario proposed by Bagheri et al. (2021) is quite limited.