A meteoroid is a small sand to boulder sized particle of debris in the Solar system. The visible path of a meteoroid that enters Earth’s atmosphere is a meteor, commonly called a shooting star or falling star. On reaching the ground, a meteor is then called a meteorite. Many meteors are part of a meteor shower. The root word meteor comes from the Greek meteoros, meaning high in the air.
During the entry of a meteoroid or asteroid into the upper atmosphere, an ionization trail is created, where the molecules in the upper atmosphere are ionized by the passage of the meteor. Such ionization trails can last up to 45 minutes at a time. Small, sand sized meteoroids are entering the atmosphere constantly, essentially every few seconds in a given region, and ionization trails can be found in the upper atmosphere continuously.
The Peekskill meteorite broke up over the United States on October 9, 1992, an event witnessed by thousands across the East Coast. The meteorite broke up over Kentucky and landed on a parked car in Peekskill, New York. The meteorite traveled northeast and had a pronounced greenish color. The meteorite has been captured on 16 different videos and remains as one of the most famous meteorite sightings.
Eyewitness accounts indicate that the fireball entry of the Peekskill meteorite started over West Virginia at 11:48 pm est. The fireball, which traveled in a northeasterly direction had a pronounced greenish colour, and attained an estimated peak visual magnitude of -13, brighter than a full moon. During a luminous flight time that exceeded 40 seconds the fireball covered a path of 450 miles.
Numerous people have over the years reported sounds being heard while bright meteors flared overhead. This would seem impossible, given the relatively slow speed of sound. Any sound generated by a meteor in the upper atmosphere, such as a sonic boom, should not be heard until many seconds after the meteor disappeared. However, in certain instances, for example during the Leonid meteor shower of 2001, several people reported sounds described as crackling, swishing, or hissing occurring at the same instant as a meteor flare. Similar sounds have also been reported during intense displays of Earth’s auroras.
Many investigators believe the sounds to be imaginary, essentially sound effects added by the mind to go along with a light show. However, the persistence and consistency of the reports have caused others to wonder. Sound recordings made under controlled conditions in Mongolia in 1998 by a team led by Slaven Garaj, a physicist at the Swiss Federal Institute of Technology at Lausanne, support the contention that the sounds are real.
How these sounds could be generated, assuming they are in fact real, remains something of a mystery. It has been hypothesized that the turbulent ionized wake of a meteor interacts with the magnetic field of the Earth, generating pulses of radio waves. As the trail dissipates, electromagnetic energy could be released, with a peak in the power spectrum at audio frequencies. Physical vibration induced by the electromagnetic impulses would then be heard if they are powerful enough to make grasses, plants, eyeglass frames, and other conductive materials vibrate. This proposed mechanism, although proven to be plausible by laboratory work, remains unsupported by corresponding measurements in the field.
Even very small meteoroids can damage spacecraft. The Hubble Space Telescope has about 572 tiny craters and chipped areas.