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Defending the Planet: How NASA Supercomputers Capture Hypothetical Asteroid Impacts

This video shows the entry, impact, and blast evolution through the first 20 minutes after impact of the hypothetical asteroid PDC 2023. The colors show temperature, where blue tones indicate cooler temperatures. The view shows a cutting plane extending about 100 kilometers (km) downrange and more than 50 km in altitude. The frame rate of the movie is adjusted to show more detail in the early phases of the entry and blast propagation. Animation credit: Michael Aftosmis, NASA/Ames

While millions of people across North America looked skyward to view the total solar eclipse in early April, scientists in the NASA Advanced Supercomputing (NAS) Division have had their eyes closer to Earth—focusing on what might occur if our planet should someday get hit by an asteroid, and what we might be able to do to mitigate the damage.

Most of the meteorites that strike Earth every day are tiny dust particles by the time they reach the surface, but larger asteroids could cause major damage to local areas or set off disasters such as tidal waves and quakes.

As part of the efforts of the NASA Planetary Defense Coordination Office to find possible threatening near-Earth objects (NEO), researchers in the NAS Division’s Computational Aerosciences Branch are developing new tools and computational fluid dynamics (CFD) methods to more accurately capture a variety of hypothetical asteroid strikes to help estimate the possibility and extent of damage such impacts could cause. NASA high-end computing resources at the NAS facility at Ames Research Center in Silicon Valley are critical to all of these projects.

Extreme Entry Exercise

Image from a simulation of a quadcopter isolated rotor in hover in ground effect.
Snapshots from a simulation of the entry, impact, and blast propagation over the first six minutes after entry of the hypothetical asteroid PDC 2023, illustrated through local Mach contours. While the entry and impact occur in only seconds, the blast takes about 12 minutes to reach the domain boundaries. Michael Aftosmis, NASA/Ames

Imagine the impact an 800-meter (2,600-foot) diameter asteroid—about the size of four big-city blocks in the U.S.—would have on Earth. That’s exactly what NAS researchers Michael Aftosmis and Wade Spurlock modeled as part of an extreme exercise for the 8th International Academy of Astronautics (IAA) Planetary Defense Conference (PDC), held in Vienna, Austria in 2023. Their high-fidelity blast wave modeling of a hypothetical asteroid named PDC 2023, performed with NASA’s Cart3D flow analysis software on the Aitken supercomputer, shows that the blast wave of a large asteroid impact of this size—while an extremely unlikely event—could potentially trigger tsunamis around the globe, like that seen in the 2022 Hunga-Tonga volcano eruption.

Blasts from the Past

Image of a cross-section showing the impact of a hypothetical kilometer-sized asteroid.
Cross-section showing the impact of a hypothetical kilometer-size asteroid, vaporizing the asteroid and some of the ground, and excavating a crater 10 km deep. Much more ground material is liberated than the mass of the asteroid. Vaporized, melted, and hot pulverized material is ejected into space. The plume expands greatly in the upper atmosphere, forming a cloud of hot material that extends hundreds of kilometers. Darrel Robertson, NASA/Ames

Using observational data from past large events—such as the 1994 Shoemaker-Levy-9 comet’s impact on Jupiter, the Chelyabinsk meteor explosion over Russia in 2013—NAS research engineer Darrel Robertson ran CFD simulations to study the potential effects of hypothetical kilometer-size asteroid impacts on Earth. Running on NASA’s Aitken, Electra, and Pleiades supercomputers, Robertson’s simulations were used by colleagues at the U.S. Geological Survey to model the effects of plume dust fallout on roads, crops, and air quality. The plumes of gas and debris not only cause hazards on the ground, but sub-micron sized particles could remain in the lower atmosphere for months or years. And, collaborators at the National Center for Atmospheric Research and the University Corporation for Atmospheric are using the results to model the blocking of sunlight and changes to the climate and effects on crops.

Models of the Future

Images comparing the blast footprints of a fixed mesh simulation and a finest adaption cyle of a hypothetical asteroid.
Blast footprints (maximum overpressure on ground throughout time) for a fixed-mesh simulation (left) and the finest adaptation cycle (right) of a hypothetical asteroid with a 50-megaton airburst. Near the blast center, 10-pounds-per-square inch (psi) contours are very similar. However, adaptive meshes carry 4-psi and 2-psi overpressure to farther distances both crossrange and downrange. Wade Spurlock, NASA/Ames

Creating accurate models of asteroid simulations eats up a lot of computing time, due to the large numerical grids (or meshes) required. With a goal to significantly reduce the computational cost and run time of future high-fidelity asteroid entry simulations, Aftosmis and Spurlock developed a CFD approach that automatically adapts the mesh to track the blast, and focusing the computational effort on the physics. When they applied this method to a full-scale, 3D unsteady asteroid blast simulation with a 50-megaton airburst, the total simulation time was dramatically reduced. Simulations were done using NASA’s Cart3D simulation code on the Aitken supercomputer, located at the energy-efficient Modular Supercomputing Facility at Ames.

These three projects are part of the NAS Division’s ongoing studies supporting the Asteroid Threat Assessment Project (ATAP) team at Ames Research Center, whose purpose is to develop models that can estimate the potential damage and devastation of an impact using probabilistic risk modeling and analysis and high-fidelity simulations. NASA’s work with other agencies and groups around the world is contributing to plans for assessing an NEO threat and developing strategies for lessening the damages, helping leaders determine the best possible actions to take in the event that one of them is on a collision course with Earth.

—Jill Dunbar, NASA Ames Research Center