High-Resolution Simulations of the Impacts of Asteroids into the Venusian Atmosphere II: 3D Models

Abstract

We compare high-resolution 2D and 3D numerical hydrocode simulations of asteroids striking the atmosphere of Venus. Our focus is on aerobraking and its effect on the size of impact craters. We consider impacts both by spheres and by the real asteroid 4769 Castalia, a severely nonspherical body in a Venus-crossing orbit. We compute mass and momentum fluxes as functions of altitude as global measures of the asteroid's progress. We find that, on average, the 2D and 3D simulations are in broad agreement over how quickly an asteroid slows down, but that the scatter about the average is much larger for the 2D models than for the 3D models. The 2D models appear to be rather strongly susceptible to the "butterfly effect," in which tiny changes in initial conditions (e.g., 0.05% change in the impact velocity) produce quite different chaotic evolutions. By contrast, the global properties of the 3D models appear more reproducible despite seemingly large differences in initial conditions. We argue that this difference between 2D and 3D models has its root in the greater geometrical constraints present in any 2D model, and in particular in the global conservation of enstrophy in 2D that forces energy to pool in large-scale structures. It is the interaction of these artificial large-scale structures that causes slightly different 2D models to diverge so greatly. These constraints do not apply in 3D and large scale structures are not observed to form. A one-parameter modified pancake model reproduces the expected crater diameters of the 3D Castalias reasonably well. c 2002 Elsevier Science (USA)

Titan impacts and escape

“…Modifications to the code are described in more detail by Korycansky et al (2002) and Korycansky and Zahnle (2003). The same modifications (multiple materials, Tillotson equation of state) have been incorporated by us in ZEUSMP2.…”

“…ZEUSMP and its predecessor versions have been used by us for a number of similar problems, such as asteroid impacts into the atmosphere of Venus and Titan (Korycansky et al, 2000(Korycansky et al, , 2002Korycansky and Zahnle, 2003, 2004, the impact of Comet Shoemaker-Levy 9 into the jovian atmosphere (Korycansky et al, 2006), and simulations of formation of the northern hemisphere dichotomy of Mars (Nimmo et al, 2008).…”

Earth Impact Effects Program: A Web-based computer program for calculating the regional environmental consequences of a meteoroid impact on Earth

“…Atmospheric entry of asteroids has been discussed in detail by many authors (Chyba et al 1993;Ivanov et al 1997;Krinov 1966;Melosh 1981;Passey and Melosh 1980;Svetsov et al 1995;Korycansky et al 2000Korycansky et al , 2002Zahnle 2003, 2004;Bland and Artemieva 2003) and is now understood to be a complex process, involving interaction of the atmosphere and fragmenting impactor in the Earth's gravitational field. For the purposes of a simple program of the type that we have created, many of the refinements now understood are too complex to be included.…”

Effect of yield curves and porous crush on hydrocode simulations of asteroid airburst

“…This approach has been used to model airbursts such as the Chelyabinsk meteor where the burst altitude was observed, or the Tunguska event where burst altitude was estimated by matching predicted ground damage to that observed [Boslough, 2014]. Korycansky et al [2002] used ZEUS to simulate airburst of asteroids in the Venusian atmosphere using a crater field on Venus for calibration/validation of their simulations. Korycansky et al [2003] examined the effect of porosity but again assumed that the asteroid had no initial cohesion.…”

“…Korycansky et al [] used ZEUS to simulate airburst of asteroids in the Venusian atmosphere using a crater field on Venus for calibration/validation of their simulations. Korycansky et al [] examined the effect of porosity but again assumed that the asteroid had no initial cohesion.…”