The word bolide is believed to have it's origins in the Greek word Bolis and has different meanings to different types of scientists. It can refer to a physical object and in that context means "missile".
It can also mean to flash or go by suddenly. So what actually is a bolide?
The International Astronomy Union can come to no agreement on what it exactly is. Is it a giant meteorite that explodes in a flash of light as it enters the Earth's atmosphere? Is it maybe a comet, with the gases and such all igniting as crashes into the planet?
It could be either or even both!
To geologists, it refers to a giant crater formed by the impact of a body of extraterrestrial origin, maybe it is alien space craft! At the United States Geological Services website, they used the term bolide "to imply that we do not know the precise nature of the impacting body...whether it is a rocky or metallic asteroid, or an icy comet" (http://woodshole.er.usgs.gov/epubs/bolide/introduction.html. This definition separates them for geologists from craters of volcanic origin or from known meteorite impacts such as the Sunset Crater in Arizona.
Why are bolides important? Should people be concerned about them? How frequently do they hit the Earth?
Bolides are definitely considered to have originated in outer space and have drastically affected the history of the planet. Some people believe bolides were responsible for the current shape of the continents and for several of the mass extinctions that have occurred in the past. Dinosaurs are believed to have been victims of a bolide.
The National Aeronautics and Space Administration has for the last several years been cataloguing space objects that could impact the Earth and cause problems in the future. They will identify them and hopefully find ways to alter their paths, preventing the death and destruction bolides have caused in the path.
Of course, this can create a problem as once they identify and approaching object, prevent it from hitting the planet, it is no longer technically a bolide. Bolides are unidentified objects that flash and form craters, remember! They are like a UFO, if you can identify it; it is no longer unidentified and no longer a UFO. Identifying a bolide, which is also unknown, witll no longer make it unknown.
Maybe that is what bolides actually are! They are crashing alien spaceships from other planets that dematerialize upon impact.
Why haven't the scientists thought of that!