Detection of a high density meteoroid on cometary orbit

Abstract

AbstractWe report a detection of a unique fireball photographed at three Czech stations of the European Fireball Network on June 1, 1997. The main exceptionality of this fireball is given by its retrograde heliocentric orbit (i= 138°) typical for comets and, at the same time, a behavior in the Earth’s atmosphere typical for the hardest component of the interplanetary matter. The spectrum of the fireball is unique by the absence of the sodium line. With the entry velocity of 65 km s−1, the meteoroid of an estimated initial mass of 0.2 kg (diameter of several centimeters) penetrated down the altitude 65 km, i.e. significantly deeper (about 25 km) than cometary meteoroids of a comparable velocity and mass. A comparison with a typical cometary meteoroid is demonstrated on anηAquarid fireball photographed one month before.The event reported is unique in decades-long records of the fireball networks. The origin of the meteoroid in the asteroid belt is highly improbable owing to the orbit. The possibility that comets contain centimeter sized compact stones is therefore suggested.