New evidence of meteoritic origin of the Tunguska cosmic body

Abstract

Diamond-lonsdaleite-graphite micro-samples collected from peat after the 1908 catastrophic blast in the Tunguska area were studied with scanning (SEM) and transmission electron (TEM) microscopy, NanoSecondary Ion Mass Spectrometry (NanoSIMS) and Х-ray synchrotron technique. The high-pressure carbon allotropes in the Tunguska samples are being described for the first time Attributing this fact to the primary inhomogeneity, and considering the microstructural features such as cracks, deformation of the crystal lattices, etc coupled with high-pressure carbon allotropes association with metals, sulfides and phosphides, and the high ratio of Fe:Ni = 22:1 suggest that the studied samples are meteorite micro-remnants.

Lonsdaleite is faulted and twinned cubic diamond and does not exist as a discrete material

“…A cylinder of high purity graphite was used as a starting material. The cylinder was enclosed in a Ta capsule, pressurized to 19 GPa and heated at 2,473 K for 5 min, the conditions that correspond to those reported by 7 , where 'retrievable hexagonal-type diamond' occurs. The temperature was monitored with a W 3 Re/W 25 Re thermocouple located axially with respect to the heater, with a junction close to the Ta capsule.…”

“…Its formation was attributed to shock-induced transformation of graphite within the meteorite upon impact with Earth, and its occurrence was used as an indicator of shock [1][2][3] . It has since been reported from several meteorites as well as from terrestrial sediments and has been attributed to asteroidal impacts, both extraterrestrial and on Earth [4][5][6][7] .…”

“…1a,b) or match those of graphite, but well-resolved X-ray reflections for lonsdaleite have not been reported. Selectedarea electron diffraction (SAED), Raman, electron energyloss spectroscopy (EELS) and high-resolution transmission electron microscopy have also been used for identification of lonsdaleite [4][5][6][7]14,15,18,23,24 ; however, interpretation of data is ambiguous (Supplementary Note 1). In spite of the many diffraction and spectroscopic studies, unambiguous data that prove the existence of lonsdaleite as a distinct material have not been reported.…”

“…These patterns are consistent with diamond projected along o0114 or o1214, respectively, although the streaking and hexagonally arranged 111 reflections are incompatible with defect-free single-crystal cubic diamond. Such data have been interpreted as evidence for 'lonsdaleite' projected along o0104 and o0014 [4][5][6][7]14,15,20 . The circularly integrated intensity profiles of these SAED patterns ( Supplementary Fig.…”

Nanodiamond-Rich Layer across Three Continents Consistent with Major Cosmic Impact at 12,800 Cal BP

“…Angular lonsdaleite crystals also formed in some impact events via shock metamorphism of graphite in the target rocks (Hough et al 1997;Koeberl et al 1997;Langenhorst et al 1998;DeCarli et al 2002;Oleinik et al 2003). Lonsdaleite grains have been reported in impact events, e.g., Ries Crater, the K-Pg event (Bunch et al 2008), and the 1908 Tunguska airburst in Siberia (Bunch et al 2008;Kvasnytsya et al 2013). Although lonsdaleite is known to be formed through shock metamorphism during surface impacts, its presence at the site of the Tunguska airburst indicates that it also can form during cosmic airbursts.…”