OAKLAND TRIBUNE, Sunday, January 8, 1995

"4.5 million-year-old meteor was fireball seen day after yule"


SACRAMENTO -- From Los Angeles to Redding, from Reno to San Francisco, they saw a brilliant fireball of blue and white and green and yellow, sparks and smoke, and they heard sonic booms over the desert.
     The meteor that illuminated California and Nevada sky at 8:15 p.m., Dec. 26 marked the end of a journey that probably began far out between Mars and Jupiter, where a collision occurred in the asteroid belt. The rocks are estimated to 4.5 million years old.
     An asteroid fell into a new orbit of the sun that happened to correspond with Jupiter's, and the great planet's gravity yanked it away onto another, final course.
     So brilliant and so widely observed was this fireball that scientists are gathering eyewitness accounts to reconstruct the orbit of this asteroid.
     "A very bright flash lit up the entire Eastern Sierra mountain range brighter than the full moon," NASA astronomer Karl Stapelfeldt, a guest at Caltech's Owens Valley Radio Observatory in Big Pine, said in a note on the Internet.
     About 90 seconds after the flash, Stapelfeldt, a member of the Hubble Space Telescope science team at Jet Propulsion Laboratory in Pasadena, heard two sharp sonic booms, "followed by a low rumbling that slowly died away."
     At NASA's Ames Research Center in Mountain View, astronomer Peter Jenniskens is especiallly interested in the possiblility that the fireball left a meteorite on the floor of the desert.
     "The most wonderful thing about a meteorite is that you have a piece of rock which is extraterrestrial, which comes from outer space, " said Jenniskens. "And these rocks have properties that are very different from rocks that we have here on Earth."
     Jenniskens is a specialist in meteor streams. He succeeded in reconstructing the orbits of two earlier fireballs -- the Glanerbrug meteor in the Netherlands in 1990 and the Mbale meteor in Uganda in 1992. Both meteors were observed by hundreds of people, and in both cases meteorites were found.
     The possibility of finding a piece of space rock that survived the Dec. 26 fireball is important not only to Jenniskens' attempt to reconstruct the orbit but to the more central scientific object of his work -- "understanding the relationship of a meteorite to an asteroid."
     "The question is, which meteorites come from what asteroids?" he said. The character and composition of a meteorite can tell scientists were in the asteroid belt it originated.
     Scientists describe the asteroid belt as a wide, thin ring of rocks formed by collisions of small planets early in the formation of the solar system. They extend from about 200 million to 325 million miles from the sun. Some are solid iron, like the core of Earth, while others are composed of iron and lighter stony material.
     Some collisions among these asteroids push them into an orbit that is in "resonance" with Jupiter's orbit. They then get pulled away.hese asteroids push them into an orbit that is in "resonance" with Jupiter's orbit. They then get pulled away.