¹Jiří Borovička,²Felix Bettonvil,³Gerd Baumgarten,⁴Jörg Strunk,⁵Mike Hankey,¹Pavel Spurný,⁶Dieter Heinlein
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13628]
¹Astronomical Institute of the Czech Academy of Sciences, Fričova 298, CZ‐25165 Ondřejov, Czech Republic
²Leiden Observatory, Leiden University, Niels Bohrweg 2, 2333 CA Leiden, the Netherlands
³Leibniz‐Institute of Atmospheric Physics at Rostock University, Schlossstraße 6, D‐18225 Kühlungsborn, Germany
⁴European Fireball Network and Arbeitskreis Meteore, D‐32049 Herford, Germany
⁵American Meteor Society LTD, 54 Westview Crescent, Geneseo, New York, 14454 USA
⁶German Fireball Network, Lilienstraße 3, D‐86156 Augsburg, Germany
Published by arrangement with John Wiley & Sons

The C1‐ungrouped carbonaceous chondrite Flensburg fell in Germany on September 12, 2019, in the daytime. We determined the atmospheric trajectory, velocity, and heliocentric orbit using one dedicated AllSky6 meteor camera and three casual video records of the bolide. It was found that the meteorite originated in the vicinity of the 5:2 resonance with Jupiter at heliocentric distance of 2.82 AU. When combined with the bolide energy reported by the United States government sensors (USGS), the preatmospheric diameter of the meteoroid was estimated to be 2–3 m and the mass to be 10,000–20,000 kg. The meteoroid fragmented heavily in the atmosphere at heights of 46–37 km, under dynamic pressures of 0.7–2 MPa. The recovery of just one meteorite suggests that only a very small part of the original mass reached the ground. The bolide velocity vector was compared with that reported by the USGS. There is good agreement in the radiant but the velocity value has been underestimated by the USGS by almost 1 km s−1.

¹Morlok, Andreas et al. (>10)
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2021.114363]
¹Institut für Planetologie, Westfälische Wilhelms-Universität Universität Münster, Wilhelm-Klemm-Strasse 10, 48149, Germany
Copyright Elsevier

We have synthesized and analyzed silicate glasses that are representative for the glasses on the surface of Mercury by mid-infrared reflectance spectroscopy, based on high-pressure laboratory experiments and the resulting compositions of the glass phase. The spectra are of interest for investigating the surface of Mercury using the MERTIS (Mercury Radiometer and Thermal Infrared Spectrometer) instrument on board of the ESA/JAXA BepiColombo mission.

Both powdered fractions and polished blocks have been analyzed. Powdered size fractions of 0–25 μm, 25-63 μm, 63-125 μm, and 125–250 μm were measured in reflectance in the thermal infrared (2–20 μm). Spectra for powdered bulk glasses (1.6 wt% – 19.0 wt% MgO) show a single, dominating Reststrahlenband (RB, 9.3–9.8 μm), a Christiansen Feature (CF; 7.6 μm – 8.1 μm), and a size dependent Transparency Feature (TF; 11.6–11.9 μm). Micro-FTIR analyses of polished blocks of glasses (3.4–26.5 wt% MgO) have characteristic bands at 7.8–8.2 μm (CF), and 9.3–9.9 μm (RB). Only few olivine crystalline features were observed.

Spectral features correlate with compositional characteristics, e.g. SiO2 content or SCFM (SiO2/(SiO2 + CaO + FeO + MgO) index. The strongest correlation between band features CF and the strong RB are with Mg/Si. No simple mixture of glass spectra from this study is able to reproduce the entire ground based spectrum of the surface of Mercury. However Mg-rich glasses reproduce identified features at 8.5 μm, 9.9 μm and 12.4 μm.