Meteor shower
Indeed, one theory proposes that the Tunguska object was a fragment of Comet Encke. This ball of ice and dust is responsible for a meteor shower called the Beta Taurids, which cascade into Earth's atmosphere in late June and July - the time of the Tunguska event.
Does Lake Cheko have anything to do with the Tunguska blast?
The absence of any crater connected with the Tunguska event has left the door open for some outlandish alternatives to the meteorite theory. A lump of anti-matter, a colliding black hole and - inevitably - an exploding alien spaceship have all been proposed as the possible source of the blast.
But in 2007, Giuseppe Longo, from the University of Bologna, Italy, and his colleagues, suggested they might have found something Leonid Kulik had missed all those years ago.
Lake Cheko does not appear on any maps of the area made before 1908; it also happens to lie North-West-West of the epicentre, on the general path taken by the impactor as it plummeted to Earth.
To Dr Longo, a radar signal from beneath the lake is suggestive of a dense object, possibly part of the Tunguska meteorite, buried about 10m down. The team plans to conduct an expedition to the area in 2009, to investigate this possibility.
"We have no positive proof it is an impact crater, we have come to this conclusion [about Lake Cheko] through the negation of other hypotheses," Dr Longo told BBC News last year.
But other researchers, including Gareth Collins and Phil Bland of Imperial College London, cast doubt on the idea Lake Cheko has anything to do with the Tunguska event.
They point to trees older than 100 years which are still standing around the rim of the lake (and, they say, should have been levelled by the impact) and the features of the lake itself, which, the researchers argue, are inconsistent with an impact origin.
From: BBC News.