RENO, Nev. – Tiny meteorites found in the Sierra foothills of northern California were part of a giant fireball that exploded over the weekend with about one-third the explosive force of the atomic bomb dropped on Hiroshima in World War II, scientists said Wednesday.
The rocks each weighed about 10 grams, or the weight of two nickels, said John T. Wasson, a longtime professor and expert in meteorites at UCLA’s Institute of Geophysics and Planetary Physics.
Experts say the flaming meteor, dating to the early formation of the solar system 4 to 5 billion years ago, was probably about the size of a minivan when it entered the Earth’s atmosphere with a loud boom early Sunday. It was seen from Sacramento, Calif., to Las Vegas and parts of northern Nevada.
An event of that size might happen once a year around the world, said Don Yeomans of NASA’s Near-Earth Object Program Office at the Jet Propulsion Laboratory in Pasadena, Calif. But most of them occur over the ocean or an uninhabited area, he said.
“Getting to see one is something special,” he said.
The meteor probably weighed about 154,300 pounds, said Bill Cooke, a specialist in meteors at NASA’s Marshall Space Flight Center in Huntsville, Ala. At the time of disintegration, he said, it probably released energy equivalent to a 5-kiloton explosion. The Hiroshima bomb was 15 kilotons.
“You don’t often have kiloton rocks flying over your head,” he said.
The friction between the rock and the air is so intense that “it doesn’t even burn it up; it vaporizes,” said Tim Spahr, director of the Minor Planet Center at Harvard University.
Wasson said one meteorite was found near the town of Coloma, about 35 miles northeast of Sacramento. “I’m sure more will be found, I’m hoping, including some fairly big pieces,” he said.
Robert Ward of Prescott, Ariz., who has been hunting and collecting meteorites around the world for more than 20 years, said he found the first piece about 10 a.m. Tuesday in between a baseball field and park on the edge of the town of Lotus, Calif.
“It was just, needless to say, a thrilling moment,” he said.
Ward and others tracked the meteorites’ possible location based on estimates by, among others, scientists with the Meteor Group at the Western University of Ontario in Canada that the fireball likely had exploded in the upper atmosphere above California’s Central Valley.