NASA@SC17

Our Planet

Asteroid Impact Risk Assessment

Overview

While many small meteors burn up harmlessly in our atmosphere every year, rare strikes from larger asteroids can cause substantial damage on the ground. To better evaluate these potential dangers, NASA’s Asteroid Threat Assessment Project (ATAP) is developing state-of-the-art asteroid impact risk models and simulations.

Project Details

ATAP researchers have developed a Probabilistic Asteroid Impact Risk (PAIR) model that efficiently analyzes millions of impact scenarios from asteroids of various sizes and properties. The model takes samples from statistical distributions of asteroid properties, models the atmospheric entry and breakup of each case, and evaluates the resulting damage at locations all over the world. Modeled hazards include blast waves and thermal radiation, tsunami inundation from ocean strikes, and global effects from large-scale impacts. While previous asteroid risk assessments have relied on estimates of average properties and damage, the PAIR model is able to capture the wide range and relative likelihoods of various damage severities.

ATAP teams also perform high-fidelity simulations to better understand the complex physics and interactions involved in atmospheric entries, impacts, and the resulting hazards. These include Cart3D computational fluid dynamics simulations of airburst blast propagation, and intensive ALE3D hydrocode simulations of entry physics, tsunami generation, and ground impact cratering. Simulation results are used to improve damage estimates for key impact scenarios and to refine the efficient analytic models used in the PAIR model.

Results and Impact

Results provided key data for NASA’s 2017 Near-Earth Objects (NEO) Science Definition Team (SDT). The SDT used current advances in NEO characterization and modeling capabilities to reevaluate which asteroid sizes pose a significant enough threat to warrant tracking, and what future survey missions may be most beneficial. The PAIR results were a major contribution to the study, and provided a significant advancement over the approach employed in the previous 2003 NEO SDT study.

The PAIR model is also at-the-ready to evaluate damage risks along specific impact corridors if a potential asteroid threat is discovered. While no actual impacts are currently expected, PAIR results have supported several impact exercises in which NASA, FEMA, DOE, and other groups use hypothetical impact scenarios to prepare for how to evaluate and respond to such a threat.

Why HPC Matters

NASA’s Pleiades supercomputer enables the PAIR model to run the millions of asteroid impact cases needed to assess the full range of potential damage and produce meaningful risk probabilities. For example, the NEO SDT study required 60 million impact cases, run in parallel on 1,600 cores, to produce converged results across the broad size ranges being considered. Supercomputing resources also allow the model to provide rapid-response assessments if a specific impact threat were to be discovered.

Because large asteroid impacts are fortunately rare, high-fidelity simulations are essential to studying the complex processes involved in atmospheric entry, impact, and the resulting hazards. A single hydrocode entry simulation can take 24,000 processor hours, while a full tsunami simulation can require 300 processors running for a month.

What’s Next

ATAP researchers continue to advance impact risk modeling capabilities based on high-fidelity simulation results and new asteroid characterization data. Future work includes modeling different asteroid structures, which can range from solid monoliths to loosely bound rubble piles, and adding mitigation modeling into the risk assessment to investigate how different deflection or civil response strategies affect damage probabilities.

More Information

Lorien Wheeler, NASA Ames Research Center
lorien.wheeler@nasa.gov
Donovan Mathias, NASA Ames Research Center
donovan.matthias@nasa.gov