No. 102: Nov-Dec 1995
When something exploded over Siberia on June 30, 1908, flattening more than 2,100 square kilometers of forest, it left no crater of consequence and no obvious pieces of itself. Scientists have claimed all along that it was a comet or asteroid that detonated in the atmosphere. A few less conservative people ventured that it was an alien spaceship that blew up! G. Longo and colleagues, Universita di Bologna, have apparently found a way to determine the true nature of this invading object. They examined the resin in the conifers surrounding the site of the blast to see if any particulate debris had been trapped in the sticky goo -- much as ancient insects have been preserved in amber.
"Longo and associates used a scanning electron microscope to examine 7,163 particles recovered from the site and from two control sites. They found anomalously high abundances of elements such as iron, calcium, aluminum, copper, gold, zinc, and oxygen in the Tunguska-site samples, strongly peaking around 1908."
Their conclusion: The impactor was a stony meteorite of normal density. (Anonymous; "Remnants of Tunguska," Astronomy, 23:26, October 1995.)