Asteroids are Stronger, Harder to Destroy

Computer modeling at Johns Hopkins finds that asteroids are stronger than we used to think and require more energy to be completely shattered.

In the early 2000s, a different research team created a computer model into which they input various factors such as mass, temperature, and material brittleness, and simulated an asteroid about a kilometer in diameter striking head-on into a 25-kilometer diameter target asteroid at an impact velocity of five kilometers per second. Their results suggested that the target asteroid would be completely destroyed by the impact.

The new model accounts for the more detailed, smaller-scale processes that occur during an asteroid collision. Previous models did not properly account for the limited speed of cracks in the asteroids.

The impacted asteroid retained significant strength because it had not cracked completely, indicating that more energy would be needed to destroy asteroids.

Icarus – A new hybrid framework for simulating hypervelocity asteroid impacts and gravitational reaccumulation.

Highlights

• This paper presents a new computational approach to investigating the consequences of major impacts into asteroids.

• The approach uses a recent model for materials under impact conditions, integrated with a long-timescale gravitational computation.

• The work provides new insights into the potential disruption of asteroids through collisions.

Abstract

We present a hybrid approach for simulating hypervelocity impacts onto asteroids. The overall system response is separated into two stages based on their different characteristic timescales. First, the short-timescale fragmentation phase is simulated using a modified version of the Tonge–Ramesh material model implemented in a Material Point Method framework. Then, a consistent hand-off to an N-body gravity code is formulated to execute the long-timescale gravitational reaccumulation calculation. We demonstrate this hybrid approach by considering the 5 km/s head-on impact of a 1.21 km diameter basalt impactor on a 25 km diameter target asteroid. The impact event resulted in the fragmentation, but not complete disruption, of the entire target. A granular core is observed at the end of the fragmentation simulations, which acts as a gravity well over which reaccumulation occurs in the N-body simulations. Our results suggest that disruption thresholds for rocky asteroids are higher when energy-dissipating mechanisms such as granular flow and pore collapse are included.

SOURCES- John Hopkins

Written by Brian Wang

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