Models for the Origin of the Current Martian Satellites
The origin of the two small prograde natural satellites of Mars may, or may not, be important in deciphering the early history of planet Mars. There have been many proposals for the origin of Phobos and Deimos but there is no generally accepted model for
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Models for the Origin of the Current Martian Satellites
The recent evidence that Phobos is made of carbonaceous chondritic material suggests that the Martian moons are captured objects and not locally formed satellites. However, as pointed out by Burns (1972, 1977, 1978) and emphasized by Pollack (1977), the low inclinations of these satellites’ orbits are very difficult to account for if they were tidally captured. And thus we propose instead that they were acquired as a result of gas drag effects in a primordial Martian nebula.—From Pollack et al. (1979, p. 608). The meager available information that is pertinent to the origin and evolution of the Martian satellites is contradictory. The known physical properties of the Martian moons (density, albedo, color and spectral reflectivity) are similar to those of many C-type asteroids, the dark ‘carbonaceous’ objects abundant in the outer belt but scarce near Mars; thus this line of physical evidence suggests that Phobos and Diemos are captured bodies. In contrast, calculated histories of orbital evolution due to tides in the planet and in the satellites indicate that these small craggy moons originated on nearly circular, uninclined orbits not far from their current positions; hence dynamicists prefer an origin in circum-Martian orbit.—From Burns (1992, p. 283). Here we use numerical simulations to suggest that Phobos and Diemos accreted from the outer portion of a debris disc formed after a giant impact on Mars. In our simulations, larger moons form from material in the denser inner disc and migrate outwards due to gravitational interactions with the disc. The resulting orbital resonances spread outwards and gather dispersed outer disc debris, facilitating accretion into two satellites of sizes similar to Phobos and Deimos. The larger inner moons fall back to Mars after about 5 million years due to the tidal pull of the planet, after which the two outer satellites evolve into Phobos- and Deimos-like orbits. The proposed scenario can explain why Mars has two small satellites instead of one large moon. Our model predicts that Phobos and Deimos are composed of a mixture of material from Mars and the impactor.—From Rosenblatt et al. (2016, p. 481). It has been proposed that Mars’ moons formed from a disk produced by a large impact with the planet. However, whether such an event could produce tiny Phobos and Diemos remains unclear. Using a hybrid N-body model of moon accumulation that includes a full treatment of moon-moon dynamical interactions, we first identify new constraints on the disk properties needed to produce Phobos and Deimos. We then simulate the impact formation of disks using smoothed particle hydrodynamics, including a novel approach that resolves the impact ejecta with order-of-magnitude finer mass resolution than existing methods. We find that © Springer Nature Switzerland AG 2021 R. Malcuit, Geoforming Mars, https://doi.org/10.1007/978-3-030-58876-2_3
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