The formation of asteroid satellites in large impacts: Results from numerical simulations

Abstract We present results of 161 numerical simulations of impacts into 100-km diameter asteroids, examining debris trajectories to search for the formation of bound satellite systems. Our simulations utilize a 3-dimensional smooth-particle hydrodynamics (SPH) code to model the impact between the colliding asteroids. The outcomes of the SPH models are handed off as the initial conditions for N-body simulations, which follow the trajectories of the ejecta fragments to search for the formation of satellite systems. Our results show that catastrophic and large-scale cratering collisions create numerous fragments whose trajectories can be changed by particle–particle interactions and by the reaccretion of material onto the remaining target body. Some impact debris can enter into orbit around the remaining target body, which is a gravitationally reaccreted rubble pile, to form a SMAshed Target Satellite (SMATS). Numerous smaller fragments escaping the largest remnant may have similar trajectories such that many become bound to one another, forming Escaping Ejecta Binaries (EEBs). Our simulations so far seem to be able to produce satellite systems qualitatively similar to observed systems in the main asteroid belt. We find that impacts of 34-km diameter projectiles striking at 3 km s−1 at impact angles of ∼30° appear to be particularly efficient at producing relatively large satellites around the largest remnant as well as large numbers of modest-size binaries among their escaping ejecta.

[1]  Alan W. Harris,et al.  Collisional evolution of asteroids - Populations, rotations, and velocities , 1979 .

[2]  Robert Jedicke,et al.  The fossilized size distribution of the main asteroid belt , 2003 .

[3]  H. Melosh,et al.  Binary Asteroids and the Formation of Doublet Craters , 1996 .

[4]  Re'em Sari,et al.  Formation of Kuiper-belt binaries by dynamical friction and three-body encounters , 2002, Nature.

[5]  Robert Jedicke,et al.  Observational Selection Effects in Asteroid Surveys , 2002 .

[6]  Andrea Milani,et al.  Asteroid Proper Elements and the Dynamical Structure of the Asteroid Main Belt , 1994 .

[7]  Clark R. Chapman,et al.  Discovery of companions to Asteroids 762 Pul-cova and 90 Antiope by direct imaging , 1999 .

[8]  S. Love,et al.  Tidal Distortion and Disruption of Earth-Crossing Asteroids , 1997 .

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

[10]  J. Chambers,et al.  The Primordial Excitation and Clearing of the Asteroid Belt , 2001 .

[11]  W. Benz,et al.  Catastrophic Disruptions Revisited , 1999 .

[12]  R. Jedicke,et al.  Observational Selection Effects in Asteroid Surveys and Estimates of Asteroid Population Sizes , 2002 .

[13]  Vincenzo Zappala,et al.  Do asteroids have satellites , 1989 .

[14]  Robert Jedicke,et al.  Collisional Models and Scaling Laws: A New Interpretation of the Shape of the Main-Belt Asteroid Size Distribution☆ , 1998 .

[15]  Harold F. Levison,et al.  The recent breakup of an asteroid in the main-belt region , 2002, Nature.

[16]  H. Melosh,et al.  The Stickney Impact of Phobos: A Dynamical Model , 1990 .

[17]  The formation of asteroid satellites in cata-strophic impacts: results from numerical simulations , 2003 .

[18]  M. Nolan,et al.  Velocity Distributions among Colliding Asteroids , 1994 .

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

[20]  George Lake,et al.  Direct Large-Scale N-Body Simulations of Planetesimal Dynamics , 2000 .

[21]  Harold F. Levison,et al.  Recent Origin of the Solar System Dust Bands , 2003 .

[22]  Daniel D. Durda,et al.  Asteroids Do Have Satellites , 2002 .

[23]  S. Love,et al.  Catastrophic Impacts on Gravity Dominated Asteroids , 1996 .

[24]  P. Tanga,et al.  Collisions and Gravitational Reaccumulation: Forming Asteroid Families and Satellites , 2001, Science.

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

[26]  D. Davis,et al.  Collisional history of asteroids: Evidence from Vesta and the Hirayama families , 1985 .

[28]  Z. Leinhardt,et al.  N-body simulations of planetesimal evolution: Effect of varying impactor mass ratio , 2001 .

[29]  P. Geissler,et al.  The Fate of Asteroid Ejecta , 2002 .

[30]  A. Cellino,et al.  The formation of binary asteroids as outcomes of catastrophic collisions , 1997 .

[31]  W. Hartmann.  Diverse puzzling asteroids and a possible unified explanation , 1979 .

[32]  Andrea Milani,et al.  The Determination of Asteroid Proper Elements , 2002 .

[33]  H. Melosh,et al.  Gravitational Aggregates: Evidence and Evolution , 2002 .

[34]  Discovery of a Loosely-bound Companion to Main-belt Asteroid (3749) Balam , 2002 .

[35]  William F. Bottke,et al.  Formation of asteroid satellites and doublet craters by planetary tidal forces , 1996, Nature.

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

[37]  E. Shoemaker.  Interpretation of Lunar Craters , 1962 .

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

[39]  John E. Chambers,et al.  Primordial Excitation and Depletion of the Main Belt , 2002 .

[40]  E. Asphaug.  Impact origin of the Vesta family , 1997 .

[41]  Douglas P. Hamilton,et al.  Dynamics of Distant Moons of Asteroids , 1997 .

[42]  R. Jedicke,et al.  The Orbital and Absolute Magnitude Distributions of Main Belt Asteroids , 1998 .

[43]  Erik Asphaug,et al.  Asteroid Interiors , 2002 .

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

[45]  P. Farinella,et al.  Collision rates and impact velocities in the Main Asteroid Belt , 1992 .

[46]  P. Farinella,et al.  Collisional origin of the asteroid families: Mass and velocity distributions , 1984 .

[47]  S. Weidenschilling.  On the Origin of Binary Transneptunian Objects , 2002 .