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Elisabetta Pierazzo

Elisabetta Pierazzo

PSI Research Report 2004

During 2004, Dr Pierazzo continued working on my 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 initial conditions required for modeling the onset and evolution of a hydrothermal system on the red planet. 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. The particular distribution of ice in the target (mixed cells versus layering) does not appear to significantly affect the overall shock decay. However, the description of the mixed material target, mixed cells of individual materials (basalt/ice) versus mixed material equation of state, may affect the overall results and requires a more detailed investigation, both theoretical and experimental. Modeling crater collapse is a necessary step to determine the final thermal state of the target underneath. 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.

Origin and Evolution of the Solar System: In collaboration with Dr. Andrew Rivkin, (MIT), Prof. Erick Asphaug (UC Santa Cruz), Dr. Fred Hörz (JSC) and Dr. Mark Cintala (JSC), Dr. Pierazzo is investigating how impacts among asteroids may affect the water distribution in the asteroidal regolith. This investigation is carried out though a combination of computer simulations, laboratory experiments, and telescopic observations. Pierazzo is also collaborating with Canup (SwRI) in the investigation of how large impacts affect water content over the age of the Solar System in planetary bodies, particularly the early Earth.

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.

Dr. Pierazzo investigation on the delivery of complex organic materials on planetary surfaces, in collaboration with Chyba (SETI Institute) has extended to the investigation of organic delivery to the surface of Mars. On Mars the low gravitational field (compared to Earth) results in an escape velocity of 5 km/s. As a result, after an impact event a significant fraction of projectile material may escape Mars gravity, especially in oblique impacts. The results of a series of high resolution 3D impact simulations with SOVA indicate that the delivery rate of surviving amino acid is significant for impact angles as low as 30° even if the majority of the projectile exceeds Mars' escape velocity. This is because the increased loss of projectile material with decreasing impact angle is counterbalanced by a weakening of the overall shock effects, which, in turn, increase the overall amino acid survival

Education: Pierazzo is leading an Education/Public Outreach effort, housed by PSI, entitled "The Explorer's Guide to Impact Craters". The main results in 2004 have been the activation of "The Explorer's Guide to Impact Craters", which is still under construction. Dr. Osinski spend a couple of weeks at the Haughton structure, where he collected samples, pictures, and movies of the area. The virtual tour to Haughton is now online, although still incomplete, and thanks to the samples brought back from Haughton, the development of the "Impact Rock Kits" is on its way.

1. Pierazzo E., Osinski G., Chuang F.: The explorer's Guide to impact craters, 2004 AGU Fall Meeting, Abst. #4451 (Dec. 13-17, 2004).

2. Pierazzo E., Artemieva N.A., Ivanov B.A.: Characterizing starting conditions for hydrothermal systems underneath Martian craters, 2004 AGU Fall Meeting, Abst #4368 (Dec. 13-17, 2004)

3. Pierazzo E.:Oceanic impacts and the environmental effects of atmospheric water injection, 2nd Int. Workshop on Water Dynamics, Sendai, Japan (Nov. 11-12, 2004).

4. Pierazzo E., Wünnemann K.: Hydrocode modeling of impact events (Invited), GSA 2004 Denver Annual Meeting, Abst. #74479 (Nov. 7-10, 2004).

5. Pierazzo E., Artemieva N.A., Ivanov B.A.: Characterizing starting conditions for hydrothermal systems underneath Martian craters, 7th Mars Crater Consortium Meeting (Oct. 7-8, 2004).

6. Artemieva, N.A., Ivanov B., Pierazzo E.: Modeling impact processes on Mars (abstract), International Mars Conference, Ischia Island, Italy (Sept. 19-23, 2004).

7. Pierazzo E., N.A. Artemieva, B.A. Ivanov: Starting conditions for hydrothermal systems underneath Martian craters: Hydrocode modeling, 35th LPSC (2004) Abst. #1352.

8. Turtle E.P., E. Pierazzo, G.S. Collins, G.R. Osinski, H.J. Melosh, J.V. Morgan, U.W. Reimold, J.G. Spray: Impact structures: What does crater diameter mean? 35th LPSC (2004) Abst #1772.

9. Ivanov B.A., N.A. Artemieva, E. Pierazzo: Popigai impact structure modeling: Morphology and worldwide ejecta, 35th LPSC (2004), Abst. #1240.

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