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Elisabetta Pierazzo

2005 Research Report

 

During 2005, Dr Pierazzo continued working on various research projects, while preparing papers and abstracts and new proposals relative to new research ideas.

Mars Research: Dr. Pierazzo and her team carried out hydrocode simulations of impacts on Mars aimed at characterizing the conditions required for modeling the onset and evolution of a hydrothermal system on the red planet. An accurate description of materials and in particular mixed targets, that is mixed cells of individual materials (basalt/ice) versus mixed material equation of state, is very important for realistic results. Much work has been devoted by the research team to materials equations of state, with the development of a basalt equation of state and of a multiphase equation of state for water. Investigation of mixed targets indicates that the particular distribution of ice in the target (mixed cells versus layering) does not appear to significantly affect the overall shock decay. High-resolution 3D SOVA simulations of the early stages of impact cratering indicate that the amount of melt generated in impacts is sensitive to the impact velocity. In particular, cometary impacts produce 2 to 3 times more melting than asteroidal impacts for roughly the same final crater. Crater collapse simulations carried out with SALEB show that the combination of shock/plastic heating and the structural uplift of initially deeper strata create a water-bearing zone at depths where water is in the liquid stability field. In the central uplift, the high temperatures cause water to evaporate (steam-driven circulation). The simulations indicate that for a mid-sized crater (rim diameter around 30 km) the hydrothermal circulation is probably restricted to a “column” contained well within the final crater.

Impacts and lithospheres: Dr. Pierazzo and her team have been investigating how target lithologies affect the impact cratering process by using high-resolution three dimensional hydrocode modeling and improved equations of state for materials of geologic interest to model specific well-studied terrestrial structures. Besides the impactor characteristics, the nature of the target material is a very important parameter in impact cratering, influencing every stage of the impact event, and beyond that, strongly affecting the surrounding environment. Recent work has involved the atmospheric penetration of a Canyon Diablo type iron asteroid to constrain the initial conditions of the impact event that produced Meteor Crater. Using the model of separated fragments combined with field evidence, they reached the important conclusion that Meteor Crater was produced by a main surviving fragment, hitting the target with relatively minor deceleration, followed by a cloud of smaller and slower fragments. Three-dimensional (3D) simulations of the initial stages of the Canyon Diablo impact event show that the depth of melting in the impact does not reach the Coconino Formation. Another terrestrial crater under investigation is Popigai, responsible for the production of widely distributed microtektites/ microkrystites.

Origin and Evolution of planetary biospheres: Dr. Pierazzo is continuing her research on the environmental and climatic effects of large impacts on the Earth. In particular, she has looked at water injection in the upper atmosphere after large oceanic impacts. In a Chicxulub-size impact it appears that the amount of water injected in the upper atmosphere is more than three times the amount of water vapor it can hold in present conditions. Furthermore, salts in oceanic water could be responsible for the injection of over 64 Gt of Cl and 4 Gt of S. The latter is about three times the amount of S injected in the upper atmosphere by the Pinatubo volcanic eruption in 1991.

Education: Pierazzo is leading an Education/Public Outreach effort, housed by PSI, entitled "The Explorer's Guide to Impact Craters". In 2005 the team completed the field work at Meteor Crater and Ries craters, with the collection of photos and movies for the development of the virtual tours that will appear in the Explorer's Guide web site. More samples have been collected for the impact rock kits, and animations of several numerical simulations have been added to the web site.

Peer-reviewed articles

Richardson J., H.J. Melosh, N.A. Artemieva, E. Pierazzo: Impact cratering theory and modeling for the Deep Impact mission: From mission planning to data analysis. Space Science Rev., 117(1-2), 241-267, 2005.

Articles in Refereed Conference Proceedings

Pierazzo E., N.A. Artemieva, B.A. Ivanov: Starting conditions for hydrothermal systems underneath martian craters: Hydrocode modeling. Large Meteorite Impacts (T. Kenkmann, F. Hörz, A. Deutsch Eds.), Geol. Soc. Am. Special Paper 384, 443-457, 2005.

Turtle E.P., E. Pierazzo, R.U. Reimold, J.G. Spray, H.J. Melosh, G. Collins, J. Morgan, G. Osinski: Impact structures: What does crater diameter mean? Large Meteorite Impacts (T. Kenkmann, F. Hörz, A. Deutsch Eds.), Geol. Soc. Am. Special Paper 384, 1-24, 2005.

Abstracts

Ivanov B.A., Artemieva N.A., Pierazzo E.: Impact cratering and material models: Subsurface volatiles on Mars, workshop on The Role of Volatiles and Atmospheres on Martian Impact Craters (2005) Abst #3015.

Pierazzo E.: Assessing atmospheric water injections from oceanic impacts, 36th LPSC (2005) Abst #1987.

Artemieva, N.A., Pierazzo E: Atmospheric fragmentation of the Canyon Diablo meteoroid, 36th LPSC (2005) Abst #2325.

Rivkin A.S., E. Pierazzo: Investigating the impact evolution of hydrated asteroids, 36th LPSC (2005) Abst. #2014.

Chuang F., E. Pierazzo, G. Osinski: The explorer's guide to impact craters, 36th LPSC (2005) Abst #2390.

 


Research Year: 
2005

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