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Elizabetta Pierazzo

2009 Annual Research Report


Impact Hazard and Environmental Consequences

Dr. Pierazzo is continuing her research on the environmental and climatic effects of large impacts on the Earth. She has teamed with scientists from the National Center for Atmospheric Research with the intent of using WACCM, the 3D atmospheric general circulation model with interactive stratospheric chemistry, to investigate the effect on atmospheric dynamics and chemistry of medium-size impacts. Initial tests have been exploring the short term effects on the dynamics and chemistry of the atmosphere of the delivery of large amounts of ocean water to the upper atmosphere during oceanic impacts. Initial results suggest that a 1-km-diameter object impacting a 4-km-deep ocean would inject enough water, NOx, as well as Br and Cl salts to cause a world wide ozone hole that can last for a few years after the impact (as shown in Fig. 1). A smaller impactor, 500 m in diameter, would cause a smaller ozone depletion which remains confined to the hemisphere of impact.



Fig. 1: Zonally averaged monthly mean differences (% from unperturbed) of atmospheric O3 column for 5 years after the impact in the central Pacific of a 1km asteroid at 18 km/s.


Impact Hydrocodes Benchmarking and Validation

Dr. Pierazzo has been leading a collective effort from the impact modeling community to uniformly compare, validate and benchmark the computer models ("hydrocodes") widely used by the impact community to model planetary scale impacts and their consequences, as well as by the defense community to model large explosions and the threat to civilization due to asteroid impact. A new validation effort is currently on the way, focusing on experimental impacts into sand. Initial results illustrate the importance of strength models in the determination of crater morphology; codes with simple or limited strength models are not capable of reproducing the experiments.



Fig. 2: Code comparison of crater profiles after about 5ms (experimental profile in red) for a 1G impact into dry sand.

Impacts and lithospheres

Dr. Pierazzo and her team continue to investigate the effect of target lithologies on the impact cratering process. The nature of the target material is a very important parameter in impact cratering, influencing every stage of the impact event, and affecting the environment locally and/or globally. Recent work consists in continuation of the investigation of the formation of Meteor Crater and the evolution of impact plumes. Three-dimensional (3D) simulations have been carried out to investigate the formation of Meteor Crater to characterize target and projectile disruption and melting. The evolution of impact plumes is often used to explain impact related material distribution that does not fit into normal ballistic transport models. On the other hand, impact plumes are very rarefied and include a small amount of all the material involved. Furthermore, studies of the Chicxulub ejecta suggest that other mechanisms, such as ballistic sedimentation, sediment degassing, water interaction, must play a role in the final transport of material from the impact point. Environmental effects of impact events depend on the size of the impact but also on the target material that is ejected in the impact. The Chicxulub impact illustrates the danger of impacts in sedimentary layers rich in carbonates and evaporates; on the other hand, besides the tsunami hazard oceanic impacts may have dramatic effects on atmospheric chemistry, affecting in particular upper atmospheric ozone.

Education

Pierazzo has been leading an Education/Public Outreach effort, housed by PSI, entitled "The Explorer's Guide to Impact Craters". Recent work includes the evaluation of the website by the Adler Education team, with suggestions to improve the effectiveness of the website. A team member, native Spanish-speaker Dr. Alexis Rodriguez, has translated the website into Spanish, and the creation of a Spanish mirror site is now completed. The first two teacher workshops entitled "Impact Craters!" were carried out in September/October 2009 and January 2010, and were received enthusiastically by a total of 20 elementary and mid-school teachers.

Papers:

1. Artemieva N.A., E. Pierazzo (2009) The Canyon Diablo impact event: 1. Projectile motion through the atmosphere. MAPS 44(1), 25-42.

2. P. Schulte, L. Alegret, I. Arenillas, J.A. Arz, P. Barton, P.R. Bown, T.R. Bralower, G.L. Christeson, P. Claeys, C.S. Cockell, G.S. Collins, A. Deutsch, T.J. Goldin, K. Goto, J.M. Grajales-Nishimura, R.A.F. Grieve, S. Gulick, K.R. Johnson, W. Kiessling, C. Koeberl, D.A. Kring, K.G. MacLeod, T. Matsui, H.J. Melosh, A. Montanari, J.V. Morgan, C.R. Neal, D.J. Nichols, R.D. Norris, E. Pierazzo, G. Ravizza, M. Rebolledo-Vieyra, W. U. Reimold, E. Robin, T. Salge, R.P. Speijer, A.R. Sweet, J. Urrutia-Fucugauchi, V. Vajda, M.T. Whalen, P.S. Willumsen (2010) The Chicxulub asteroid impact and mass extinction at the Cretaceous-Paleogene boundary. Science. In Press (March 5 issue).

3. Ivanov B., H.J. Melosh, E. Pierazzo: Basin-forming impacts: Reconnaissance modeling (2010) in Large Meteorite Impact and Planetary Evolution IV, W.U. Reimold, R. Gibson, Eds., Geological Society of America Special Paper 465. In Press.

4. Pierazzo E., Melosh H.J. (2010) Extraterrestrial causes of environmental catastrophes. In J.A. Matthews Ed. Handbook of Environmental Change (Sage Publ. London). Invited. In Press (mid-2010).

Abstracts:

1. Pierazzo E., R. Garcia, D. Kinnison, D. Marsh: Quantifying the perturbation of atmospheric chemistry from medium-size asteroid impacts in the ocean, 41st LPSC (2010), Abst. #2445.

2. Pierazzo E., G.S. Collins, K.A. Holsapple, K.R. Housen, D.G. Korycansky, C.S. Plesko, M.C. Price, K. W√ľnnemann: Impact hydrocode benchmark and validation project: impacts into cohesionless soil, 41st LPSC (2010), Abst. #2048.

3. Croft S.K., E. Pierazzo, T. Canizo. L.A. Lebofsky: The Explorer's Guide to Impact Craters: an interactive website and rock kit for outreach and professional development workshops for middle school science teachers, 41st LPSC (2010), Abst. #1460.

4. Lebofsky L.A., S.W. Anderson, L.F. Bleamaster, T.L. Canizo, S.K. Croft, D.A. Croft, S. Kortenkamp, E. Pierazzo: Professional Development Workshops for K-8 Teachers at the Planetary Science Institute, 41st LPSC (2010), Abst. #1192.

5. Pierazzo E., R.R. Garcia, D.E. Kinnison, D.R. Marsh: Quantifying the perturbation of atmospheric chemistry from medium-size asteroid impacts in the ocean. 2009 AGU Fall meeting (2009), Abs. #710875.

6. Pierazzo E. (2009) Understanding environmental effects associated with impact events. 2009 Joint Assembly meeting, Toronto, May 24-27. Abst. #1485. Invited.

7. Lebofsky L.A., L.F. Bleamaster, T.L., Canizo, S.K. Croft, D.A. Crown, E. Pierazzo (2009) Professional development workshops for K-8 teachers at the Planetary Science Institute. 2009 AGU Fall meeting.

8. Croft S.K., E. Pierazzo, T. Canizo, L.A. Lebofsky (2009) An impact cratering interactive website used for outreach and in professional development workshops for middle school science teachers. 2009 AGU Fall Meeting.

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