Call the UFOlogists!

Some Italian geoscientists think they have discovered the spot in Siberia where the so-called "Tunguska event" occurred - the 1908 explosion, probably caused by a meteorite, which devastated a huge area and lit up the sky as far away as London. It's also a favorite incident for UFO conspiracy theorists.

Anyhow, the scientists have discovered a lake that might actually be an asteroid impact crater:

A University of Bologna team says a lake near the epicentre of the blast may be occupying a crater hollowed out by a chunk of rock that hit the ground. Lake Cheko - though shallow - fits the proportions of a small, bowl-shaped impact crater, say the Italy-based scientists. Their investigation of the lake bottom's geology reveals a funnel-like shape not seen in neighbouring lakes.

But don't close the books on the conspiracies:

A geophysics survey of the lake bed has turned up an unusual feature about 10m down which could either be compacted lake sediments or a buried fragment of space rock.

Or the mothership!