One scientist thinks the Tunguska meteor was hit by a UFO, to save Earth from even more serious damage than it caused:

"Most scientists think the blast was caused by a meteorite exploding several miles above the surface. But [Dr. Yuri]Labvin thinks quartz slabs with strange markings found at the site are remnants of an alien control panel, which fell to the ground after the UFO slammed into the giant rock.


"'We don't have any technologies that can print such kind of drawings on crystals,' Labvin told the Macedonian International News Agency. We also found ferrum silicate that can not be produced anywhere, except in space.'"


Read more: [link to www.foxnews.com]

I also saw older GLP threads about UFOs hitting meteors (from 2009, for example), but I don't see them now. I'll try again...