Re: Where do US Astronomers stand on the origins of the Tunguska event?

Italians in the 90's said mineral evidence in the area suggested a meteor/asteroid origin. Russian teams, one using Ground Penetrating Radar in 2010 and another using mathematical modeling in 2008 say "nope, it was for sure a comet". Kelly 2009 said the "sky glow" effect suggest comets as well. Does the US astronomical community have a particular take on the current body of evidence, one way or the other?

There is no consensus. The matter is also confused by our newer understanding of both asteroids and comets, which suggests that the two can overlap each other substantially in their properties. For instance, we observe asteroids that appear to be made up of gravitationally bound rubble piles rather than monolithic structures, and we observe comets that don’t have a high content of volatiles- more like “snowy dirtballs” and less like “dirty snowballs”. Some asteroids appear chemically similar to the rocky material found in some comets.

At this point, what we know of the dynamics of the impact event can be reasonably modeled or explained by either an asteroid or a comet, in both cases assuming realistic physical properties for those bodies.

An event the size of the Tunguska impact almost certainly produced some material on the ground- embedded in trees, below shallow craters or impact pits, in lakes, trapped in ice. It is likely that with continued investigation, material will be recovered (some claim it already has, but that remains unsettled). However, even mineralogical examination of debris may not conclusively settle the question. Currently, there are no well accepted mineralogical or chemical characteristics that absolutely distinguish comets and asteroids from each other. Of course, as we visit and sample more of each, that may change.