She and her team hunted down image negatives containing fireballs stored at the German Aerospace Center in Augsburg. After digitizing the images, the researchers estimated various parameters related to the incoming meteors, such as their masses, shapes, speeds and entry angles. Using this data, the researchers identified a dozen events that most likely produced sizable meteorites. Before 1976 only three had occurred.
The team reconstructed the trajectory of each of those three fireballs and calculated where the meteorites would most likely be found. There was only one match to the location where the Ischgl meteorite was recovered. This led researchers to conclude that the fireball that crossed the horizon in the early morning hours of November 24, 1970 gave birth to the Ischgl meteorite.
“This matched exactly,” Dr. Gritsevich said.
She and her colleagues calculated that the incoming meteor hit Earth at a speed of about 45,000 miles per hour. This is fast but well within the range of meteoroids born in the solar system, Dr. Gritsevich said. Something from beyond the solar system, however, would have traveled much faster, he added.
The team estimated that the meteoroid that produced the 1970 fireball orbited the sun relatively close to Earth. It probably didn’t come from the main asteroid belt between Mars and Jupiter, which is the source of many meteoroids, Dr. Gritsevich said.
Linking a meteorite to where it was born is important, said Marc Fries, a planetary scientist at NASA’s Johnson Space Center in Houston who was not involved in the research. “It goes from just being a rock that you find on the ground to a rock that comes from a specific place in the solar system,” he said. To date, the orbits of approximately 50 meteorites have been determined; Ischgl is the third oldest of them.
