The Mysterious Siberian Explosion of 1908

Did aliens save planet in 1908?
Russians say they have found spaceship debris

Members of a Russian scientific team researching the site of the Tunguska meteorite crash of 1908 say they have found remnants of an extraterrestrial spacecraft, report a variety of Russian news agencies.

The object appeared to be a large metallic block, according to the reports. The researchers chipped off a piece of the object and will now test its composition.

The alien idea sounds like it's from a movie. My theory is that time travel is involved instead. (Anyone read Michael Crichton's Sphere or saw the movie?)

Update: I read another article on this topic today:
Russians add new twist to old UFO myth
Tale of 1908 Tunguska explosion gets even more tangled

It didn’t do the new Russian UFO story’s credibility much good that it first appeared on the pages of the newspaper Pravda on Tuesday. In Soviet days, Pravda was the propaganda arm of the Soviet Communist Party, but under new management, it became a tabloid-style scandal sheet with a special penchant for wild paranormal tales.

I guess enquiring minds want to know. In any case, the newly found debris could have come from 1960's Russian spacecraft:

Sassen was referring to a flight on Dec. 22, 1960, meant to carry two dogs into space. According to “Challenge to Apollo,” NASA’s definitive history of the space race, "the payload landed about 3,500 kilometers downrange from the launch site in one of the most remote and inaccessible areas of Siberia, in the region of the Podkamennaya Tunguska River close to the impact point of the famed Tunguska meteorite."

And although it's long been suggested that the explosion could have been caused by a comet, a meteorite is the more likely culprit.