The Proceedings of the Eighth International Conference on Creationism (2018)

the Nice migration. This change was made by modifying input parameters such as the eccentricities of the planetesimal orbits, starting Saturn, Uranus, and Neptune slightly closer together, and slightly adding to the mass of the planetesimal disk (Gomes, 2005, p. 467). However, a more recent paper raises questions as to whether the Nice model can explain the Late Heavy Bombardment. Kaib and Chambers (2016) model both the inner planets and the outer planets in the same extended Nice model simulations. Most prior studies examine only the outer planets in the Nice model simulations. With the terrestrial planets included it was found that the orbits of Jupiter and Saturn become more eccentric due to the global instability which scatters planetesimals in the outer solar system. The outer planets affect each other’s orbits in this scenario because of the mutual resonances between them. The instability in the outer solar system causes the precession rate to change in Jupiter’s orbit and this makes Jupiter pass through resonances with the terrestrial planets. The effect of this is to make the inner planet orbits more eccentric than the actual orbits today, especially Mercury and Venus. Thus, changes in the orbits of the outer planets in the Nice model could conceivably affect Earth. Thus, the authors of this study argue that the planetesimal instability of the Nice model does not explain the Late Heavy Bombardment and that the instability must have occurred earlier before the terrestrial planets had completed their formation. 3. The Protoplanetary Disk The Grand Tack and Nice models depend critically on the protoplanetary disk of gas and dust that the planets form from. The so-called Minimum Mass Solar Nebula (MMSN) used for the past 30 years assumes the outer planets formed at their current locations. Thus, scientists are aware of the need to modify the MMSN model to be appropriate for the new planet migration models. An attempt to do this was made by Desch, (2007). The planets were assumed to start in orbital positions as in the Nice model, then the necessary mass surface density profile for the disk was estimated as a function of distance. The resulting power law derived by Desch has a surface density nearly 10 times that of the original MMSN at 5.45 A.U. (Jupiter) and nearly 4 times that of the original MMSN at 22 A.U. (the vicinity of Neptune late in the Nice migration). This denser disk seems to work well in Desch’s approach for the accretion of the outer planets, because it is a long- lived disk. However, it leads to a serious problem. In the Desch disk, the density is so great that Jupiter migrates inward rapidly by the Type III mechanism and spirals into the Sun in only a few hundred years! The other outer planets also all spiral into the Sun in less than 20,000 years (Crida, 2009). Crida (2010) makes the statement that “I would claim that a new Solar Nebula consistent with the Nice model is still to be built” (p. 222). Thus, unresolved questions remain regarding how the disk can provide enough material for the gas giants to form and also support orbit migration in the right manner to lead to the planets as we find them today. CONCLUSION The Grand Tack and Nice models are considered to be very successful in explaining a number of major characteristics of our solar system. However, these models require many special conditions that are chosen by the investigator. They involve a prescribed sequence of events that includes four different mechanisms of planet orbit migration, Type I, Type II, planetesimal scattering, and planet-planet resonances. Though the Grand Tack and Nice models employ methods that have been applied in extrasolar planet research, no extrasolar planetary system has been proposed to involve all four of these migration mechanisms. Many special conditions are input into the simulations by the investigator to make the scenario succeed. In many ways the end result is in mind as the conditions of the simulation are started. This could be considered inappropriate investigator interference since in the real primordial solar system, there would be no agent to set up the proper conditions. For example, the extremely compact extent of the protoplanetary disk, compared to real observed disks, is unrealistic. The protoplanetary disk assumed in the Grand Tack and Nice models is only approximately 30 to 40 A.U. in radius. But observed debris disks around other stars are commonly much larger. Though the physics of planet migration may be valid, there is reason to doubt whether the conditions necessary for orbit migration can plausibly exist in real disks. For our solar system the entire process seems implausibly fortuitous. The author does not accept that orbit migration of planets occurred in our solar system. Instead supernatural creation seems necessary. It could be argued that even if our solar system did form from such a complex planet migration process it would be evidence of intelligent design. The migration simulations, rather than giving evidence of the means of formation of our solar system, should be viewed as giving information about cause and effect relationships in the solar system. Jupiter, with its large mass and strategic placement just past 5 A.U. has a stabilizing effect on both the inner and outer planets. The planets as we find them today are in orbits that are quite stable and orbit resonance relationships are not significant. The Grand Tack and Nice models also deal with broad patterns in the solar system such as the distribution of the various types of asteroids in the asteroid belt and the trans-Neptunian belt. But there are unique qualities of various bodies in the solar system that are not explained by these new models because planet migration is not relevant to those features. Examples of this would be the peculiar spin axes of Venus and Uranus. Also, the rings of the outer planets would have to be viewed as having formed after most of the migration was completed in the Nice model. There has been some research on forming the so-called “irregular” moons of the outer planets under the Nice scenario (Nesvorny, Vokrouhlicky, and Morbidelli 2007). However, many moons in the solar system have very “regular” circular orbits, they are not significantly eccentric or inclined, compared to their planet. Some moons could form early prior to migration and survive the migration of the planet, but it seems doubtful to the author that their final orbits would be nearly circular and coplanar. It is also worth noting that in running the same simulations over and over the same result is not obtained on each run. In some runs of the Grand Tack model one of the four inner planets can be ejected from the system (most frequently Mercury). Indeed, in the Grand Tack some planet embryos or small planets could have fallen into the Sun. Another issue is the final eccentricities and inclinations of the planets. During migration, the migrating planets have higher eccentricities than the actual planets today. It is assumed that these somewhat more eccentric orbits would be Spencer ◀ Origin of our solar system with planet migration ▶ 2018 ICC 79