There's a story on the Tunguska Event at Popular Mechanics.
A study suggests that it was caused by a comet that broke off a piece in the atmosphere over the region while the rest of the comet left the atmosphere and carried on back into space. The fireball was caused by hydrogen gas released by the comet, which was previously dissolved in the comet's ice.
Some points about this story:
It's really cool. If we could (as they think they might have done) track a comet that had previously hit earth - just wow.
It's almost certainly not true. It's guess piled on guess piled on supposition.
That it probably isn't true is not a criticism. The story quotes another Russian scientist as being "impressed but not convinced". Me too. Just showing that the theory is consistent with the (little) evidence we have is worthwhile. Some researchers might argue that existing evidence is not consistent with the theory. Some will look for new evidence. If new evidence is found which is consistent with the theory, that will strengthen it.
Imagine if the theory had some obvious political relevance. How would the process work then?
The paper is on arxiv.org