Mid-Infrared spectroscopy of impactites from the Noerdlinger Ries impact crater

• Main Authors: Morlok, A, Stojic, A. N, Dittmar, I, Hiesinger, H, Tiedeken, M, Sohn, M, Weber, I, Helbert, J
• Format: Journal Article
• Language: English
• Published: 04-01-2023
• Subjects: Physics - Earth and Planetary Astrophysics; Physics - Geophysics
• DOI: 10.48550/arxiv.2301.01683

Icarus (2016), Volume 264, p. 352-368 This study is part of an effort to build a mid-infrared database (7-14micron)
of spectra for MERTIS (Mercury Radiometer and Thermal Infrared Spectrometer),
an instrument onboard of the ESA/JAXA BepiColombo space probe to be launched to
Mercury in 2017. Mercury was exposed to abundant impacts throughout its
history. This study of terrestrial impactites can provide estimates of the
effects of shock metamorphism on the mid-infrared spectral properties of
planetary materials. In this study, we focus on the Noerdlinger Ries crater in
Southern Germany, a well preserved and easily accessible impact crater with
abundant suevite impactites. Suevite and melt glass bulk samples from Otting
and Aumuehle, as well as red suevite from Polsingen were characterized and
their reflectance spectra in mid-infrared range obtained. In addition, in-situ
mid-infrared spectra were made from glasses and matrix areas in thin sections.
The results show similar, but distinguishable spectra for both bulk suevite and
melt glass samples, as well as in-situ measurements. Impact melt glass from
Aumuehle and Otting have spectra dominated by a Reststrahlen band at 9.3-9.6
micron. Bulk melt rock from Polsingen and bulk suevite and fine-grained matrix
have their strongest band between 9.4 to 9.6 micron. There are also features
between 8.5 and 9 micron, and 12.5 - 12.8 micron associated with crystalline
phases. There is evidence of weathering products in the fine-grained matrix,
such as smectites. Mercury endured many impacts with impactors of all sizes
over its history. So spectral characteristics observed for impactites formed
only in a single impact like in the Ries impact event can be expected to be
very common on planetary bodies exposed to many more impacts in their past. We
conclude that in mid-infrared remote sensing data the surface of Mercury can be
expected to be dominated by features of amorphous materials.