The origin of the Moon and the single-impact hypothesis,II |
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| Institution: | 1. Department of Prehistory and Archaeology, University of Seville, María de Padilla S/N, 41004 Sevilla, Spain;2. Department of Prehistory, Archaeology, Social Anthropology and Historiographic Sciences and techniques, University of Valladolid, Pz/ del Campus S/N, 47011 Valladolid, Spain;3. Centre for Nuclear Science and Technology, IST, University of Lisbon, E.N. 10 ao km 139,7, 2695-066 Bobadela LRS, Portugal;4. Centre for Archaeology, University of Lisbon, Alameda da Universidade 1600-214 Lisboa, Portugal;5. Andalusian Centre for Ibearian Archaeology, University of Jaén, Paraje Las Lagunillas s/n, Jaén, Spain;1. Groupe de Spectrométrie Moléculaire et Atmosphérique, UMR 7331, CNRS, Université de Reims Champagne-Ardenne, Campus Sciences Exactes et Naturelles, BP 1039, Reims 51687, France;2. JPL, Nasa-caltech, Pasadena, United States |
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| Abstract: | This is the second paper devoted to the numerical study of planetary collisions as a possible scenario for forming the Moon. We present a series of nine simulations of a collision between the protoearth and an impactor of various sizes. The mass ratio between the protoearth and the impactor ranged from 0.1 to 0.25. We were able to model both planets with iron cores, having modified our smoothed particle hydrodynamics code to allow the inclusion of up to 10 different material types. Two different relative velocities at infinity for the impactor were considered: ν∞ = 0 km/sec and ν∞ = 10 km/sec. We show that for a low-velocity collision and an impactor in the mass range 6.5 × 1026 ≤ Mimpactor ≤ 8.2 × 1026 g, more than a lunar mass of iron-poor material is thrown into orbit. For an impactor with a mass within this range, the ejected mass that goes into orbit is for the most part divided comparably into material orbiting inside the Roche limit and into material orbiting outside the Roche limit. This material is either spread out in the form of a disk, or, for a relatively narrow range of masses toward the lower end of the range, clumped into an object of about lunar mass beyond the Roche limit. For impactors more massive than about 8.2 × 1026 g we found that there is too little mass thrown into orbit. For very small mass impactors well over a lunar mass is placed in orbit, but a large amount of it is iron. In the high-velocity range we did not find a possible mass range for the impactor that would lead to the formation of an iron-poor disk massive enough to form the Moon. |
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