DOI: 10.5061/dryad.8sf7m0czx
title: Simulation data from: A systematic survey of moon-forming giant impacts. II: Rotating bodies

description: In the leading theory of lunar formation, known as the giant impact
 hypothesis, a collision between two planet-size objects resulted in a
 young Earth surrounded by a circumplanetary debris disk from which the
 Moon later accreted. The range of giant impacts that could conceivably
 explain the Earth-Moon system is limited by the set of known physical and
 geochemical constraints. However, while several distinct Moon-forming
 impact scenarios have been proposed---from small, high-velocity impactors
 to low-velocity mergers between equal-mass objects---none of these
 scenarios have been successful at explaining the full set of known
 constraints, especially without invoking one or more controversial
 post-impact processes. Allowing for pre-impact rotation of the colliding
 bodies has been suggested as an avenue which may produce more promising
 collision outcomes. However, to date, only limited studies of pre-impact
 rotation have been conducted. Therefore, in the second paper of this
 series, we focus on pairwise impacts between rotating bodies. Using
 non-rotating collisions as a baseline, we systematically study the effects
 of rotation on collision outcomes. We consider nine distinct rotation
 configurations and a range of rotation rates up to the rotational
 stability limit. Notably, we identify a population of collisions that can
 produce low post-impact angular momentum budgets and massive, iron-poor
 protolunar disks. Furthermore, even when pre-impact rotation is included,
 we demonstrate that the canonical Moon-forming impact can only generate
 sufficiently massive protolunar disks in the presence of excessive
 post-impact angular momentum budgets; this casts doubt on the canonical
 impact scenario.
description: The data consists of initial conditions and simulation outputs
 from 3D hydrodynamic simulations performed with Gasoline.
description: # Simulation Data from: A Systematic Survey of Moon-Forming Giant Impacts.
 II: Rotating bodies
 [https://doi.org/10.5061/dryad.8sf7m0czx](https://doi.org/10.5061/dryad.8sf7m0czx) ## Description of the data and file structure The data consists of initial conditions and simulation outputs. ### Naming convention of directories The directory names are constructed from the relevant pre-impact parameters of the simulation. Example: DD_J1000_G0100_V01000_B07202_OMEGA0900 * DD: Orientation of the angular momentum vectors, can be any of DD, DN, DU, ND, NN, NU, UD, UN, UU * J1000: Total angular momentum in units of the Earth-Moon angular momentum. Read as 1.000 JEM * G0100: Impactor-to-target mass fraction gamma. Read as 0.100 * V01000: Asymptotic relative velocity at infinity in units of the mutual escape velocity of the two bodies. Read as 0.1000 vesc * B07202: Asymptotic impact paramter at infinity in units of the gravitational focusing radius. Read as 0.7202 Rgrav * OMEGA0900: Angular velocity of the rotating bodies in units of the critical angular velocity. Read as 0.900 Omegacrit ### Files and variables Each directory in the data set corresponds to a simulation. Each directory contains the following files: * collision.param: Gasoline parameter file (text file) * collision_result.csv: Analysis results (csv file) * collision.std: Initial condition (tipsy file) * collision.std.grp: Group finder result of the initial condition (tipsy array file) * collision.std.layers: Layer identification (tipsy array file) * collision.std.mat: Material numbers for the intitial condition (tipsy array file) * collision.std.stat: Group finder statistics of the initial condition (text file) * outcome.std: Collision result (tipsy file) * outcome.std.analysis: Verbose analysis output (text file) * outcome.std.grp: Group finder result of the collision result (tipsy array file) * outcome.std.stat: Group finder statistics of the collision result (text file) * proj.bic: Projectile file (tipsy file) * targ.bic: Target file (tipsy file) Simulations that result in a merger additionally contain these files: * outcome_ftvd_5.pdf: Plot of the disk finder result (pdf file) * outcome_post_50.pdf: Plot of the collision outcome (pdf file) * outcome_post_5.pdf: Plot of the collision outcome, zoomed in (pdf file) * outcome.std.canup: Result of the Canup disk finder (tipsy array) * outcome.std.disk: Result of our disk finder (tipsy array) Simulations that needed to be run for longer than the standard simulation time additionally contain one or more sets of these files (where 0X00 stands for the step): * collision_result_extended_0X00.std.csv: Analysis results of the extended result * extended_0X00_ftvd_5.pdf: Plot of the disk finder result (pdf file) * extended_0X00_post_50.pdf: Plot of the collision outcome (pdf file) * extended_0X00_post_5.pdf: Plot of the collision outcome, zoomed in (pdf file) * extended_0X00.std: Collision result (tipsy file) * extended_0X00.std.analysis: Verbose analysis output (text file) * extended_0X00.std.canup: Result of the Canup disk finder (tipsy array) * extended_0X00.std.disk: Result of our disk finder (tipsy array) * extended_0X00.std.grp: Group finder result of the extended result (tipsy array file) * extended_0X00.std.stat: Group finder statistics of the extended result (text file) ### Units The unit system used in this data set is defined by the following values * Length unit: 1 Earth radius * Velocity unit: 1 km/s * Gravitational constant G = 1 In these units, 1 Earth mass is equal to 62.5476 mass units, while 1 time unit corresponds to 1.77 hours. ## Code/software The file is packed in a two-stage process: * The raw directory structure is packed without compression using winrar to make use of its file-level deduplication, reducing the file size from 122 GB to 82 GB * The resulting rar file is then compressed using lzma2 which results in a file size of 34GB In order to unarchive the data set, issue the following commands in a linux environment (unxz and unrar are freely available for most linux distributions): unxz -k Meier_2024_Collision_data.rar.xz unrar x Meier_2024_Collision_data.rar A total of 238 GB of free space is needed for this process. Tipsy files can be viewed using tipsy (free software) or pynbody (a python package available through pip).