Abstract
The Tunguska airburst occurred in the area of the Podkamenaya Tunguska River on June 30, 1908 and it was most likely caused by the impact of the Tunguska cosmic body (TCB). It is not clear what the origin of the TCB was as no impact craters or possible body remains have been found to date.
We studied the possible molten fragments of the TCB found in lacustine sediments of Zapovednoye Lake, a water body which is located ~60 km west from the airburst epicentre. Lake sediment cores which were retrieved from the lake contained an event layer dated to 1908-1910 CE.
This layer was of anomalous elemental composition and contained microscopical molten fragments. Sediment samples were measured using gamma spectrometry for the specific activity of 210Pb, 137Cs, and 226Ra isotopes, as well as XRF and SME.
Radioisotope activities revealed the age of the event layer which is consistent with the year 1908 CE. Magnetic spherules (MSPs) were rich in iron and most of them were found at depth corresponding to the event layer.
We targeted our research on magnetic grains and observed Fe-rich MSPs of potential impact or extraterrestrial origin.