SPH calculations of Mars-scale collisions: The role of the equation of state, material rheologies, and numerical effects

Abstract We model large-scale ( ≈ 2000 km) impacts on a Mars-like planet using a Smoothed Particle Hydrodynamics code. The effects of material strength and of using different Equations of State on the post-impact material and temperature distributions are investigated. The properties of the ejected material in terms of escaping and disc mass are analysed as well. We also study potential numerical effects in the context of density discontinuities and rigid body rotation. We find that in the large-scale collision regime considered here (with impact velocities of 4 km/s), the effect of material strength is substantial for the post-impact distribution of the temperature and the impactor material, while the influence of the Equation of State is more subtle and present only at very high temperatures.

[1]  M. Zuber,et al.  The Borealis basin and the origin of the martian crustal dichotomy , 2008, Nature.

[2]  R. Canup,et al.  ON A GIANT IMPACT ORIGIN OF CHARON, NIX, AND HYDRA , 2011 .

[3]  M. Ćuk,et al.  Making the Moon from a Fast-Spinning Earth: A Giant Impact Followed by Resonant Despinning , 2012, Science.

[4]  O. Aharonson,et al.  Mega-impact formation of the Mars hemispheric dichotomy , 2008, Nature.

[5]  Martin Jutzi,et al.  SPH calculations of asteroid disruptions: The role of pressure dependent failure models , 2015, 1502.01860.

[6]  Sarah T. Stewart,et al.  Dynamic fault weakening and the formation of large impact craters , 2009 .

[7]  J. Monaghan.  Smoothed particle hydrodynamics , 2005 .

[8]  Steven W. Squyres,et al.  The martian hemispheric dichotomy may be due to a giant impact , 1984, Nature.

[9]  J. Stadel,et al.  Numerical aspects of giant impact simulations , 2017, 1701.08296.

[10]  W. Benz.  An introduction to computational methods in hydrodynamics , 1991 .

[11]  Willy Benz,et al.  Collisional stripping of Mercury's mantle , 1988 .

[12]  J. Makino,et al.  Density Independent Smoothed Particle Hydrodynamics for Non-Ideal Equation of State , 2013, 1307.0916.

[13]  J. H. Tillotson.  METALLIC EQUATIONS OF STATE FOR HYPERVELOCITY IMPACT , 1962 .

[14]  F. Nimmo,et al.  Implications of an impact origin for the martian hemispheric dichotomy , 2008, Nature.

[15]  R. Canup.  Forming a Moon with an Earth-like Composition via a Giant Impact , 2012, Science.

[16]  W. Benz,et al.  A hit-and-run giant impact scenario , 2012, 1207.5224.

[17]  Coupling SPH and thermochemical models of planets: Methodology and example of a Mars-sized body , 2017, 1710.03250.

[18]  H. Melosh.  Impact Cratering: A Geologic Process , 1986 .

[19]  Piet Hut,et al.  A hierarchical O(N log N) force-calculation algorithm , 1986, Nature.

[20]  R. Canup,et al.  Simulations of a late lunar-forming impact , 2004 .

[21]  William H. Press,et al.  Numerical recipes in C. The art of scientific computing , 1987 .

[22]  Erik Asphaug,et al.  Impact Simulations with Fracture. I. Method and Tests , 1994 .

[23]  S. L. Thompson,et al.  Improvements in the CHART D radiation-hydrodynamic code III: revised analytic equations of state , 1974 .

[24]  William R. Ward,et al.  The Origin of the Moon , 1976 .

[25]  J. Monaghan.  Smoothed particle hydrodynamics , 2005 .

[26]  H. J. Melosh,et al.  A hydrocode equation of state for SiO2 , 2007 .

[27]  C. Loore.  Late stages of stellar evolution : computational methods in astrophysical hydrodynamics : proceedings of the Astrophysics School II, organized by the European Astrophysics Doctoral Network at Ponte de Lima, Portugal, 11-23 September 1989 , 1991 .

[28]  Hidenori Genda,et al.  Formation of Phobos and Deimos via a giant impact , 2015, 1503.05623.

[29]  Keith A. Holsapple,et al.  Modeling asteroid collisions and impact processes , 2015, 1502.01844.

[30]  W. Benz,et al.  The Origin of Mercury , 2007 .

[31]  W. Benz,et al.  Simulations of brittle solids using smooth particle hydrodynamics , 1995 .

[32]  J. Monaghan,et al.  A refined particle method for astrophysical problems , 1985 .

[33]  Gareth S. Collins,et al.  Modeling damage and deformation in impact simulations , 2004 .

[34]  R. Canup,et al.  A Giant Impact Origin of Pluto-Charon , 2005, Science.

[35]  Numerical aspects of giant impact simulations , 2017 .

[36]  F. A. Seiler,et al.  Numerical Recipes in C: The Art of Scientific Computing , 1989 .

[37]  Richard A. Schultz,et al.  Large impact basins and the mega-impact origin for the crustal dichotomy on Mars , 1988 .

[38]  O. Aharonson,et al.  Geophysical consequences of planetary-scale impacts into a Mars-like planet , 2011 .

[39]  Erik Asphaug,et al.  Origin of the Moon in a giant impact near the end of the Earth's formation , 2001, Nature.

[40]  William K. Hartmann,et al.  Satellite-Sized Planetesimals and Lunar Origin , 1975 .

[41]  Erik Asphaug,et al.  Similar-sized collisions and the diversity of planets , 2010 .