Earth Impact Effects Program: A Web-based computer program for calculating the regional environmental consequences of a meteoroid impact on Earth

Question

1. What are the contributions in "Earth impact effects program: a web-based computer program for calculating the regional environmental consequences of a meteoroid impact on earth" ?

2. What have the authors stated for future works in "Earth impact effects program: a web-based computer program for calculating the regional environmental consequences of a meteoroid impact on earth" ?

3. What is the fundamental quantity in assessing the environmental consequences of an impact?

4. What is the recurrence interval for an impact of this sort?

Accepted Answer

Earth Impact Effects Program: A Web-based computer program for calculating the regional environmental consequences of a meteoroid impact on Earth Gareth S. COLLINS,1 * H. Jay MELOSH,2 and Robert A. MARCUS2 1Impacts and Astromaterials Research Centre, Department of Earth Science and Engineering, Imperial College London, South Kensington Campus, London, SW7 2AZ, UK 2Lunar and Planetary Laboratory, University of Arizona, 1629 East University Boulevard, Tucson, Arizona 85721–0092, USA * Corresponding author.. This paper details the observations, assumptions and equations upon which the program is based.. It describes their approach to quantifying the principal impact processes that might affect the people, buildings, and landscape in the vicinity of an impact event and discusses the uncertainty in their predictions.. This paper details the observations, assumptions and equations upon which the program is based.. It describes their approach to quantifying the principal impact processes that might affect the people, buildings, and landscape in the vicinity of an impact event and discusses the uncertainty in their predictions.

Accepted Answer

The authors anticipate that within the field of impact cratering their program will serve the function of providing a quick assessment of the hazard risk for potential future impact scenarios and enable those studying particular terrestrial impact events to estimate the regional environmental consequences associated with the impact.. The authors welcome any suggestions for improvements or additions to the algorithm presented here.

Accepted Answer

The most fundamental quantity in assessing the environmental consequences of the impact is the energy released during the impact, which is related to the kinetic energy of the impactor E before atmospheric entry begins.

Accepted Answer

Iron asteroids represent only ~5% of the known NEOs; therefore, the real recurrence interval for an impact of this sort is ~20 times longer.

Accepted Answer

To estimate the peak overpressure for crater-forming impacts, the authors assume that the impact-generated shock wave in the air is directly analogous to that generated by an explosive charge detonated at the ground surface (surface burst).

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The only noticeable consequences from this scale of impact would be from seismic shaking, which would be most obvious around 40 sec after the impact occurred.

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the duration of irradiation is proportional to E1/3, and the thermal exposure required to ignite a given material is proportional to E1/6.

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Using a mean ejection angle of 45° to the Earth’s surface allows us to estimate the approximate arrival time of the bulk of the ejecta.

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The authors estimate the thickness of ejecta at a given distance from an impact by assuming that the material lying above the pre-impact ground surface is entirely ejecta, that it has a maximum thickness te = htr at the transient crater rim, and that it falls off as one over the distance from the crater rim cubed:(43)The power of −3 is a good approximation of data from explosion experiments (McGetchin et al. 1973) and a satisfactory compromise for results from numerical calculations of impacts and shallow-buried nuclear explosions, which show that the power can vary between −2.5 and −3.5.

Accepted Answer

The spreading velocity at airburst multiplied by the time to impact is added to the breadth of the swarm to estimate the dispersion of what will be a strewn field on the surface.

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The final rim height of the crater, which is required for their estimate of the breccia-lens thickness in simple craters (above) is found by inserting r = Dfr/2 into Equation 31:(48*)

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The equations for effective seismic magnitude use curves fit to empirical data of ground motion as a function of distance from earthquake events in California (Richter 1958, p. 342).

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The central difficulty in deriving an accurate estimate of the final crater diameter is that no observational or experimental data exist for impact craters larger than a few tens of meters in diameter.

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To account for the impact-energy dependence of the thermal exposure required to ignite a material (or cause skin damage), the authors use a simple scaling law.

Accepted Answer

The three impacts the authors will consider are a 40-m diameter iron asteroid (density = 8000 kg m−3) impacting at 20 km s−1 into a sedimentary target (density = 2500 kg m−3), which is the approximate scenario of the event that formed Barringer Crater in northern Arizona; a 1.75-km diameter stony asteroid (density = 2700 kg m−3) impacting at 20 km s−1 into a crystalline target (density = 2750 kg m−3), which corresponds approximately to the magnitude of the impact event that formed the Ries crater in Germany; and an 18-km diameter stony asteroid also impacting at 20 km s−1 into a crystalline target, which represents a reasonable estimate of the scale of the Chicxulub impact event in the Gulf of Mexico.

Accepted Answer

Small meteoroids are often ablated to nothing during this phase, but in the current program implementation, the authors ignore ablation on the grounds that it seldom affects the larger impactors that reach the surface to cause craters.

Earth Impact Effects Program: A Web-based computer program for calculating the regional environmental consequences of a meteoroid impact on Earth

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Most frequently asked questions

1. What are the contributions in "Earth impact effects program: a web-based computer program for calculating the regional environmental consequences of a meteoroid impact on earth" ?

2. What have the authors stated for future works in "Earth impact effects program: a web-based computer program for calculating the regional environmental consequences of a meteoroid impact on earth" ?

3. What is the fundamental quantity in assessing the environmental consequences of an impact?

4. What is the recurrence interval for an impact of this sort?

5. What is the way to estimate the peak overpressure for crater-forming impacts?

6. What would be the noticeable consequences from the impact?

7. What is the thermal exposure required to ignite a given material?

8. How do the authors estimate the arrival time of the bulk of the ejecta?

9. How do the authors estimate the thickness of ejecta at a given distance from an impact?

10. What is the swarm's dispersion at impact?

11. How do the authors determine the rim height of a crater?

12. What is the commonly accepted figure for effective seismic magnitude use curves?

13. What is the difficulty in deriving an accurate estimate of the final crater diameter?

14. How do the authors calculate the thermal exposure required to ignite a material?

15. What is the approximate scenario of the impact event that formed Barringer Crater in northern Arizona?

16. What is the reason for the ablation of small meteoroids?

Figures

Citations

A 500-kiloton airburst over Chelyabinsk and an enhanced hazard from small impactors

Rayleigh-Taylor and Richtmyer-Meshkov instabilities: A journey through scales

Structural geology of impact craters

The interaction of the cretaceous-tertiary extinction bolide with the atmosphere, ocean, and solid earth

Physics of meteor generated shock waves in the Earth’s atmosphere : A review

References

Physics of Shock Waves and High-Temperature Hydrodynamic Phenomena

Extraterrestrial Cause for the Cretaceous-Tertiary Extinction

Physics of Shock Waves and High-Temperature Hydrodynamic Phenomena

Book Review: Impact cratering - A geologic process. H. J. Melosh. The Clarendon Press, Oxford university press, New York, 1989, 245p. + vii, $45.00 (ISBN-0-19-504284-0)

Book Review: Impact and Explosion Cratering. Proceedings of the Symposium on Planetary Cratering Mechanics. Pergamon Press, 1977, 1299 pp., US $150.00, £98.00, ISBN 0-08-022050-9

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