[PAE22-P03] Prevalence and extent of magma oceans in rocky bodies
キーワード：magma ocean, accretion, planetary formation, planetary diversity
It is well accepted that the Earth and most rocky bodies in the Solar System went over a magma ocean stage during and immediately after their accretion (e.g., Tonks and Melosh, JGR 1993; Elkins-Tanton, Annu. Rev. Earth Planet. Sci. 2012). Based on this, it is generally assumed that magma oceans are common and widespread throughout the Universe, and that they exist throughout all the accretion stage of different bodies. Another common assumption made is that magma oceans extend deep inside the bodies and cover their entire surface. However, how frequent magma oceans are, and how deep do they extend, is not well constrained. In this work, we aim to understand the factors that control the formation duration of magma oceans, and the conditions that lead to deep ones. Understanding these questions is of extreme importance, as a magma ocean sets up the conditions for future mantle dynamics and tectonic activity, the composition of the atmosphere, and the possibility for the existence of oceans, and life.
We present a model that computes the extent of melting in a planet by taking into account the input of energy from impacts during accretion, and output of energy from radiative cooling of a magma ocean. We test two ways of taking into account the energy input due to impacts: (1) a parameterized distribution of impactors’ distribution and energy, following Shibaike et al., (Icarus, 2016) and (2) using frequency and intensity of impacts extracted from N-body simulations (e.g., de Vries et al., PEPS 2016). Furthermore, we will show how the results are affected by: (1) how opaque the atmosphere is, (2) different impacts histories and accretion times, and (3) how the energy of a single impact is distributed in the interior of the body, i.e, does the melt generated spread out evenly across the globe as assumed by, for example, de Vries et al. (PEPS 2016), or the magma ocean generated has different depths at different locations around the planet as predicted by Reese and Solomatov (Icarus, 2006) for higher solid mantle viscosities.
We present a model that computes the extent of melting in a planet by taking into account the input of energy from impacts during accretion, and output of energy from radiative cooling of a magma ocean. We test two ways of taking into account the energy input due to impacts: (1) a parameterized distribution of impactors’ distribution and energy, following Shibaike et al., (Icarus, 2016) and (2) using frequency and intensity of impacts extracted from N-body simulations (e.g., de Vries et al., PEPS 2016). Furthermore, we will show how the results are affected by: (1) how opaque the atmosphere is, (2) different impacts histories and accretion times, and (3) how the energy of a single impact is distributed in the interior of the body, i.e, does the melt generated spread out evenly across the globe as assumed by, for example, de Vries et al. (PEPS 2016), or the magma ocean generated has different depths at different locations around the planet as predicted by Reese and Solomatov (Icarus, 2006) for higher solid mantle viscosities.