Asteroid impact risk

Abstract

Asteroid impacts are a hazard to human populations. A method to assess the impact risk of hazardous asteroids was developed in this work, making use of the universal concept of risk culminating in the Asteroid Risk Mitigation Optimization and Research (ARMOR) tool. Using this tool, the global spatial risk distribution of a threatening asteroid can be calculated and expressed in the units of expected casualties (= fatalities). Risk distribution knowledge enables disaster managers to plan for a potential asteroid impact through identification of high risk regions and estimation of total risk as a scalar value. Expressing the risk in terms of expected casualties would allow the placement of the asteroid threat on the same scale as other human hazards. Thus, this unit provides an accessible way of defining thresholds for asteroid threat response protocols, of communicating the threat utilizing a new hazard scale, and of allocating adequate resources to address the hazard by comparison with other natural disasters. To accomplish risk estimation, vulnerability models were needed that relate the severity of impact effects (wind blast, overpressure shock, thermal radiation, cratering, seismic shaking, ejecta out-throw, and tsunami) on the human population and a novel comprehensive suite of such models were derived and presented. The need for high fidelity impact effect and vulnerability modelling, as opposed to a simplified, impact location based approach, for risk estimation of a specific asteroid threat was analysed and confirmed. Subsequently, the method of ARMOR was applied to asteroid 2015 RN35 to produce an example risk distribution output. Additional analysis shows that the general impact location distribution of asteroids is approximately uniform, confirming, for the first time, a common assumption made in planetary defense. Extensive global simulations were performed utilizing an artificial sample of 50,000 impactors with sizes up to 400m to identify which impact effects are most hazardous to the human population. Aerothermal effects are most hazardous while tsunamis only contribute moderately to the overall hazard. The average land impactor is an order of magnitude more dangerous than a similar water impactor and asteroids smaller than 50-60m (density ≈ 3100 kg/m3) are expected to airburst rather than reach the surface. Furthermore, the average loss estimate for asteroid impactors enables fast threat analysis of newly discovered asteroids and helps determine the asteroid size that contributes most to the residual asteroid impact risk. These results provide new insights to inform efficient preparation for a future asteroid threat. In the future, ARMOR can be used to perform on-ground risk driven asteroid detection mission design which would reduce risk of an incoming asteroid progressively and this is not accomplished with current methods.

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Identifiers

ORCID for Clemens, M. Rumpf: orcid.org/0000-0003-2530-4046

ORCID for Hugh Lewis: orcid.org/0000-0002-3946-8757

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