The first strand of the project was to reproduce and complement an existing age for an impact structure with an age determined using state-of-the-art techniques in geochronology of zircon. This was done for the Lappajärvi impact structure, Finland, which has a diameter of approximately 23 km. Sub-millimeter-scale zircon grains were separated from rocks from the impact structure. The grains were imaged and characterized using state-of-the-art scanning electron microscopy (SEM) techniques and were then dated using uranium–lead radiometric dating. The new age obtained for this impact structure was actually slightly older than the previously accepted age of the structure and offered insights into the cooling of impact structures and the accurate dating of impact events. The results were published in Geochimica et Cosmochimica Acta.
After demonstrating the utility of the newly established protocol, the next strand saw application of the method to another impact structure in Finland, the Sääksjärvi impact structure. The work led to a new age for the impact structure, which was tens to hundreds of millions of years older than previous estimates for the age of the structure. This resolved issues with the previously suggested younger ages and demonstrated that dating small impact structures may help constrain the timing of other geological processes in the Earth’s crust. The results were published in the Journal of the Geological Society, London.
In addition to the mineral zircon, the project also involved work on the mineral apatite. Apatite and related minerals are much more common than zircon in rocks from the Moon and Mars and so understanding how apatite responds to the impact events is important for dating impacts and other events on these planetary bodies. Using the same imaging and characterization techniques earlier applied to zircon, it was shown that a hypervelocity impact can induce recrystallization and chemical changes in apatite. These findings were published in Geology.
Exploitation of results: The routines for dating impact structures with zircon that were developed in the course of the project are now being applied to impact structures around the world in collaboration with researchers globally. The researcher has also been working with a group of researchers who focus on the evolution of the Moon and Mars, and the insights gained in this project have also benefitted the interpretation of data from lunar and Martian samples. Furthermore, that the routines developed during the project have been published a peer-reviewed articles means that other researchers can now apply, and build on, this methodology in other laboratories, further expanding the impact of the project.
Dissemination of results: At the time of final report writing, results from the project had been published in four peer-reviewed publications. It is envisaged that at least four further publications will come from the project. The results were also disseminated to the scientific community at conferences, including the Annual Meeting of the Meteoritical Society (Moscow, Russia; 2018), the Lunar and Planetary Science Conference (Houston, Texas, USA; 2019) and the Large Meteorite Impacts Conference (Brasilia, Brazil; 2019). Invited lectures were given at a range of institutions. Results were disseminated to the general public through outreach events including the “Borrow a researcher” event run by the host institution in association with European Researchers’ Night.
