Lake Cheko and the Tunguska event: Impact or non-impact?

Several lines of evidence were presented in Gasperini et al. [Terra Nova (2007), vol. 19, pp. 245–251] suggesting that Lake Cheko, a small lake close to the alleged epicentre of the 1908 Tunguska Event, might be a secondary impact crater. Collins et al. [Terra Nova (2008), this volume] argue against this hypothesis. We reply here arguing in favour of an impact origin for Lake Cheko.