Periodic Reporting for period 1 - IMPACT (Physics of Impact Cratering Collapse)
Reporting period: 2016-12-15 to 2018-12-14
A clear understanding of how complex craters form is essential in numerous aspects of planetary geology, including investigation of stratigraphy and composition of the near-surface structure of planetary bodies, derivation of reliable crater-based chronologies, and unravelling the bombardment history on the Earth-Moon system, and the origin and evolution of life on our planet.
The overall objective of the project was the improving of the current understanding of the mechanics acting during the final stages of the impact cratering process, and it was fulfilled through a multidisciplinary approach including laboratory experiments and numerical modelling. Both the methodologies were required to comprehensively address the challenge of crater collapse. Laboratory experiments take advantages of direct measure of material response to fluidization, while numerical modelling can simulate assesses the individual effect of any variable on crater formation.
Numerical modelling was based on a systematic study varying projectile radius (0.1 to 9 km) and BM parameters. The target was assumed Moon-like, with a dunitic mantle overlaid by a 50 km-thick gabbroic anorthosite or basaltic crust. The results showed that (i) decay times produce the largest variations in the final crater morphometry, and whether or not a central uplift forms; (ii) the best fit was obtained for longer lasting decay times (with corresponding depth-to-diameter ratio smaller than ~0.8); (iii) impacts with same kinetic energy occurring in different terrains (Maria or Highlands) can have a difference up to 25% in the d/D ratio. I then derived scaling laws to relate final crater diameter to the transient one, which is fundamental in many questions like the determination of the impact energy, and the original depth of excavation. I found that the model-derived scaling laws are sensitive to the BM parameters and the target material, and predict a much larger (up to 30%) final crater than the one suggested by observation for any given transient crater, suggesting that a definite revision of available scaling laws is required for planetary science.
These results were presented in a number of dissemination and communication activities, including three seminars at my Host Institute, and eleven international conferences (with five oral contributions). The final results of the project are matter of two peer review papers in phase of completion. Furthermore, the weekly opportunity provided by seminars at the Host Institute and partner universities (FU) allowed frequent meetings with researchers from other institutes. This guaranteed an active debate and comparison between the own fields of expertise, and the mutual benefits of the new findings.
The innovative research program contributed to the Host Institute’s reputation as regards the high quality research environment and the excellent infrastructures. This ensured the development of new synergies with universities and other institutes (the project engaged the attention for a future collaboration regarding laboratory experiments under vacuum), to attract Bachelor and Master students (MfN had a visiting student of Dr. Melosh, the worldwide standing expert on impact cratering), to promote new fund raising for PhD students and Postdocs, and to foster scientific matters among people (educational programs at MfN). Museum like the ""Rieskrater Museum"" (Nördlingen, Germany) can benefit from the up-to-date findings to actualise the collection, enabling better exchange with relevant scientific institutions (Ries crater was training location for the Apollo astronauts), and increasing interest for the museum visitors. Furthermore, the nature of impact craters favoured collaborations in the space exploration programme (ESA HERA space mission), which will provide benefits as regards new research cooperation, educational program, and new technologies for commercial applications."