A strange stone kept in a box is linked to a meteorite that fell 54 years ago

Thousands of meteorites have been found on Earth, but most of them are shrouded in mystery. These rocks come from space, but tracing their exact origins in the solar system or even beyond is difficult without knowing their flight paths.

But now, researchers believe they have linked a meteorite discovered in the Austrian Alps decades ago to the bright light emitted by a space rock rapidly passing through our planet’s atmosphere. Linking a meteorite to its original “fireball” is rare, and these results demonstrate the utility of combining older data sets, the research team suggests. Their findings were Published in the Journal of Meteoritics and Planetary Science In May.

In 1976, Josef Pfefferle, a forest ranger, was clearing the remains of an avalanche near the Austrian village of Ischgl when he noticed a strange-looking stone. He brought a handful of the black stone back home and put it in a box.

Thirty-two years later, Mr. Pfefferle heard a news story about a meteorite discovered in Austria and thought that perhaps his strange rock had also come from space. He decided to bring his rock to the university for analysis.

Mr. Pfefferle’s discovery turned out to be a meteorite, and relatively large, weighing more than two pounds. Moreover, its exterior showed that it had fallen to Earth only shortly before Mr. Pfefferle picked it up.

“It was a very fresh meteorite,” said Maria Gritsevich, a planetary scientist at the University of Helsinki in Finland, who led the recent study. “It was very well preserved.”

Dr. Gritsevich and his colleagues speculated that if the Ishgl meteorite had fallen to Earth relatively recently, its arrival might have been captured on film. A network of 25 sky-view cameras spread across southern Germany had been collecting long-exposure photographs of the night sky since 1966. By the time the network stopped working in 2022, it had recorded more than 2,000 fireballs.

“It made the most sense to detect it from the fireballs that were recently observed in this region,” Dr. Gritsevich said.

He and his team searched through negatives of fireball images stored at the German Aerospace Center in Augsburg. After digitizing the images, the researchers estimated various parameters about the incoming meteors, such as their mass, size, velocity and angle of entry. Using that data, the researchers zeroed in on a dozen events that likely produced meteors of sizable size. Only three occurred before 1976.

The team reconstructed the trajectories of all three of those fireballs, and calculated where the meteorites were most likely to be found. Only one matched the location from which the Ishgall meteorite was recovered. This led the researchers to conclude that a fireball moving at low altitude across the horizon in the early morning hours of November 24, 1970, produced the Ishgall meteorite.

“It matches perfectly,” Dr. Gritsevich said.

He and his colleagues calculated that the incoming meteor fell to Earth at a speed of about 45,000 miles per hour. That’s a fast speed, but within the range of meteors born in the solar system, Dr. Gritsevich said. On the other hand, any meteor coming from beyond the solar system would be traveling much faster, he said.

The team speculated that the meteorite that created the 1970 fireball once orbited the sun relatively close to Earth. Dr. Gritsevich said it probably did not come from the main asteroid belt between Mars and Jupiter, which is the source of many meteorites.

It’s important to relate a meteorite’s place of birth to its location, said Mark Fries, a planetary scientist at NASA’s Johnson Space Center in Houston, who was not involved in the study. “It goes from just being a rock that you find on the ground to being a rock that comes from a very specific place in the solar system,” he said. To date, The orbits of about 50 meteoroids have been determined; Ischgl is the third oldest of them.

However, the case of the Ishgal meteorite is not closed yet, said Peter Brown, a planetary scientist at Western University in Ontario, who was not involved in the research. After all, there’s always the possibility that the meteorite may have been on Earth’s surface for more than six years, he said. The alpine environment in which it fell may have preserved the rock quite well.

“It may have literally been there for decades, possibly centuries,” Dr. Brown said.

Still, he said, there’s a good story here: “It’s great to be able to show that there’s value in this old data.”

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