New Evidence of High-Temperature, High-Pressure Processes at the Site of the 1908 Tunguska Event: Implications for Impact and Airburst Phenomena: Supporting Information

We report diverse shock-metamorphosed and melted grains from the 1908 airburst site in Russia. Analysis of samples from a rimmed crater-like feature near the epicenter revealed microspherules, carbon spherules, glass-like carbon, and melted minerals. In addition, quartz grains exhibit high-temperature melting and shock metamorphism, including planar deformation features (PDFs) and planar fractures (PFs), with some showing glass-lined internal fractures and melted silica coatings. These grains indicate high shock pressures (≥2 GPa) and temperatures (≥1710°C), consistent with proposals that fragments from the Tunguska airburst struck the Earth’s surface at velocities sufficient to produce shocked quartz. These findings advance our understanding of airburst/impact mechanics, but because few people have ever observed a dangerous airburst like Tunguska, very little is known about them. Lacking sufficient real-world data, scientists should continue modeling these dangerous low-altitude airbursts to understand them better. The Tunguska event is a valuable case study demonstrating the urgent need to improve our planetary defense strategies.