Planetary Defense

The Near-Earth Object Preparedness Strategy and Action Plan is a document that is updated every few years as we learn more about Near-Earth Objects, impact hazards, and disaster mitigation strategies.  Goal 2 of this plan focuses on modeling the effects of an asteroid striking the Earth, as well as the effects of using spacecraft missions to prevent such a strike. The Asteroid Impact Modeling Working Group focuses primarily on this goal. During the Asteroid Impact Modeling Working Group meeting, participants discussed the wide range of techniques that can be used to model the many hazards associated with asteroid impacts. Presenters shared their updates in using terrestrial analogs to simulate asteroid impacts, mission-based science and observations, and the continued development of models to predict the effects of impacts.

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There are many terrestrial analogs that we can use to understand some of the effects of an asteroid strike. For example, an asteroid impact into the ocean can cause a tsunami. We can use real-world tsunami to understand different scenarios resulting from the locations of asteroid impacts. Atmospheric disturbances from actual observations over the past few years can also be used to understand how asteroids can affect our atmosphere, for example the Hunga Tonga eruption that caused an atmospheric wave. These atmospheric waves can interact with oceans on the opposite side of the Earth to cause what are called meteotsunami, or tsunami with meteorological origins (click on the word meteotsunami for more information). Many organizations study these effects, providing a wealth of data, and people working for these organizations can provide expertise and resources to understand potential impacts. 

There are many mitigation strategies that under development for potentially hazardous asteroids, when they’re detected. Domestic and international partners occasionally convene asteroid deflection exercises to simulate an asteroid impact and evaluate the different ways to handle a potential strike. Many groups also study the ways that the asteroid can be deflected to prevent a strike. For example, missions such as the recent Double Asteroid Redirect Test (DART) provide valuable information about how much energy it takes to alter an asteroid’s orbit. 

A look to the future

Asteroid impacts are relatively rare, but it is only a matter of time before a large one happens again, and the risks are great enough that we need to be ready. The USGS and partners all over the world study potentially dangerous objects to understand how big they are and when they may come close to Earth.  Interagency exercises are held to go through new scenarios and workshop potential risks from a wide variety of asteroid hazards. Collaboration and community involvement, particularly from global communities, will be important for planning and response to future potentially hazardous impacts. Data sharing will be an important factor moving forward, and more work will be conducted on how to effectively collect and share data quickly.

The more we know about impact risks, the better we can prepare mitigations to defend against them, but data collection takes a lot of time and resources. Information from ground-based facilities (like the asteroid type and location), input from spacecraft flyby missions (like the size, shape, and composition), and important rendezvous missions (which can provide more detailed information about the shape, mass, surface characteristics, and material properties) will increase our knowledge about potentially hazardous impactors. As we are able to send more missions to different types of asteroids and comets, we get better data and can better tune our models to inform future hazard assessments. Building databases and data servers helps support the development and integration of models. It’s all hands on deck for the future of asteroid impact assessment!