Elizabetta Pierazzo

2010 Research Report

During 2010, Dr. Pierazzo continued working on various research projects:

Impact Hazard and Environmental Consequences

 Dr. Pierazzo is continuing her research on the environmental and climatic effects of medium-size impacts on the Earth in collaboration with scientists from the National Center for Atmospheric Research. The study combines simulations with the shock physics code SOVA, to evaluate the injection of material into the atmosphere, and simulations using the climate system model CESM (Community Earth System Model), to characterize the perturbation of atmospheric chemistry. CESM consists of 4+ geophysical component models (atmosphere, land, ocean, sea ice, land ice) on potentially different grids that exchange boundary data with each other via communication with a coupler. For this study, we used the Whole Atmosphere Community Climate Model (WACCM) as the atmospheric component of CESM. WA

CCM is one of a few high-top atmospheric general circulation models that incorporate a fully interactive chemical mechanism (65 species) that can track the chemical consequences of impact-produced water vapor, nitric oxide (NO), and halogens (Cl and Br) into the middle atmosphere. 

We modeled the impact of idealized spherical asteroids 500m, 700m, 1km and 2km in diameter, reaching the lower atmosphere with velocities of 12, 18 (most probable), and 25 km/s at an impact angle of 45° from the surface. The fraction of water vaporized in the impact is determined by the volume of ocean water shocked above 20 GPa. Large amounts of water are injected in the upper atmosphere  over a region that can extend horizontally up to a thousand km. The amount of vapor increases significantly with impactor size and impact velocity. Although the impacts affected the ocean crust, no crustal material is ejected in the upper atmosphere by the impacts, and only a small component of projectile is entrained in the expansion plume. We assume that liquid water is removed on a short timescale, and is not chemically active. Figure 1 shows the amount of water vapor injected in the upper atmosphere by oceanic impacts of asteroids between 500m and 2km in diameter. For comparison, the water vapor injected by a 1km diameter comet impacting at 25km/s and 45° is shown as an asterisk. Following the approach of Birks et al. [7] we then estimated amounts of impact released NO_Y, Cl_Y and Br_Y as fractions of water vapor released in the impact, as described in Pierazzo et al. (2010).

The impact perturbation for a 1km asteroid was introduced on January 1, 2000, at different latitudes in the Pacific Ocean: at the equator, in the sub-tropics, at 30°N and 30°S, and at high southern latitudes, 50°S. To investigate potential effects of seasonality, the equatorial perturbation was also investigated for a July impact. Results suggest that mid-latitude oceanic impacts of asteroids 1 km in diameter can produce a significant, global perturbation of upper atmospheric chemistry, including multi-year ozone depletion comparable to ozone hole records registered in the mid-1980s and 1990s.  Asteroids 500 m in diameter cause limited perturbation of upper atmospheric chemistry mostly confined to the hemisphere in which the impact occurred (Pierazzo et al., 2010). However, even for the larger impactors, impact location affects the extent of atmospheric perturbation (Pierazzo et al., 2011). This is evident in Figure 2, showing depletion with respect to the unperturbed case of zonally averaged montly means of atmospheric ozone column for a 1km asteroid impacting at 18km/s,. High latitude impacts cause atmospheric perturbations that is mostly confined to the hemisphere of impact, while atmospheric perturbations from medium (30°) to low latitude impacts spread to both hemispheres, thus having a global effect. Maximum perturbation occurs for equatorial impacts. Upper atmospheric ozone concentration shows seasonal variability, especially at high latitudes. The overall effect, however, is not significant.

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. During the past year we focused on building a website that is going provides the results of current (and future) validation and benchmark efforts. The website, hosted by PSI, is still under construction, but already available at: http://psi.edu/impact_code_validation/.

Education

This year has seen the conclusion of the 2^nd institutional E/PO effort lead by Pierazzo and centered on impact cratering. In May 2010, Pierazzo and collaborators held one more “Impact Craters!” teacher workshops, and developed the first PSI based podcast, featuring Bill Hartmann chatting about impact cratering. The grant allowed also the purchase of some equipment needed to produce podcasts, giving PSI the capability of producing podcasts ‘in-house.’

Furthermore, as part of the new PSI-based E/PO effort, Pierazzo was charged with the acquisition of a new set of 8 meteorite rock kits, which were first used as part of the newly developed asteroids and meteorites teacher workshop, held in Oct/Nov. 2010.

Papers 

1.   Pierazzo E., Garcia R.R., Kinnison D.E., Marsh D.R., Lee-Taylor J., Crutzen P.J. Ozone perturbation from medium-size asteroid impacts in the ocean. Earth Planet. Sci. Lett., 299, 263-273, 2010. doi:10.1016/j.epsl.2010.08.036 

2.   Ivanov B., H.J. Melosh, E. Pierazzo: Basin-forming impacts: Reconnaissance modeling. In Large Meteorite Impact and Planetary Evolution IV, W.U. Reimold, R. Gibson, Eds., Geological Society of America Special Paper 465, 29-50, 2010.

3.   Schulte P., 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^: The Chicxulub asteroid impact and mass extinction at the Cretaceous-Paleogene boundary. Science, 327, 1214-1218, 2010. doi: 10.1126/science.1177265 

Abstracts

1.     E. Pierazzo, B.A. Ivanov: Melting of Permafrost on Mars in the formation of large impact craters. 2010 AGU Fall Meeting (2010). Abst.  #953491.  Invited.

2.     E. Pierazzo, R. Garcia, D. Kinnison, D. Marsh, J. Lee-Taylor, M. Mills: Atmospheric ozone perturbation from oceanic asteroid impacts: Seasonal and zonal effects. 2010 AGU Fall Meeting (2010). Abst. #962384.

3.     N. Artemieva, Pierazzo E.: Projectile material in Meteor Crater, European Plan. Sci. Conf. 2010, Vol. 5, Abst. #182.

4.     Pierazzo E., Garcia R.R., Kinnison D.E., Marsh D.R., Lee-Taylor J., Crutzen P. : Ozone Perturbation from Medium-Size Asteroid Impacts in the Ocean.15^th Annual CESM Workshop, Breckenridge, Colorado.

5.     Garcia R., Pierazzo E., Kinnison D., Marsh D.: Quantifying the perturbation to atmospheric chemistry from medium-size asteroid impacts in the ocean, Meteoroids 2010 (Breckenridge, CO), Invited.  

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

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

8.     Croft S.K., E. Pierazzo, T. Canizo. L.A. Lebofsky: 1.   The Explorer’s Guide to Impact Craters: an interactive website and rock kit for outreach and professional development workshops for middle school science teachers, 41^st LPSC (2010), Abst. #1460.

2.   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, 41^st LPSC (2010), Abst. #1192.