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We experimentally discovered that Al2O3 and MgO exhibit well-pronounced nanometric modifications on the surfaces when irradiated under grazing incidence with 23 MeV I beam, in contrast to normal incidence irradiation with the same ion beam when no damage was found. Moreover, ions in these two materials produce notably different structures: grooves surrounded with nanohillocks on MgO surfaces vs. smoother, roll-like discontinuous structures on the surfaces of Al2O3. To explain these results, detailed numerical simulations were performed. We identified that a presence of the surface inhibits recrystallization process, thereby preventing transient tracks from recovery, and thus forming observable nanopatterns. Furthermore, a difference in the viscosities in molten states in Al2O3 vs. MgO explains the differences in the created nanostructures. Our results thus provide a deeper understanding of the fundamental processes of surface nanostructuring, potentially allowing for controlled production of periodic surface nanopatterns.

The paper presents the summary data of the authors' research within the framework of the OLIMPIYA project (the Russian acronym of {\bf OLI}viny iz {\bf M}eteoritov --- {\bf P}oisk tyazholykh {\bf I} sverkhtyazholykh {\bf YA}der / Olivines from meteorites: Search for heavy and superheavy nuclei) and results of track analysis for heavy cosmic ray nuclei (\emph{Z} = 26--129) in olivine crystals from meteorites using an original processing technique. A total of 21,743 tracks of nuclei heavier than iron have been identified in meteoritic matter to date to form the largest database within this charge range. The database includes three tracks of superheavy nuclei with the lifetimes of about a few decades, which can be considered as direct experimental evidence for the existence of natural superheavy nuclei from the "island of stability". Comprehensive comparative analysis of data from two meteorites with different cosmic ray exposure ages, Marjalahti (from 178 to 205 Myr) and Eagle Station (from 35 to 71 Myr), is presented for the first time. The results are discussed within the existing concepts of nuclei formation in astrophysical processes., Comment: 13 pages, 4 figures, 1 table