Around 1:25 A.M. local time Monday, a bright green fireball shot across the Midwest, setting off a sonic boom that shook homes below and amazed anyone who was awake to witness it.
The brief flash came from a meteor, National Weather Service meteorologist Jeff Last tells Merrit Kennedy at NPR. But it is "relatively rare to see one this vivid," he says. Reports pored into the American Meteor Society, from Iowa to New York—even some Canadians reported seeing the blast.
NASA meteor expert William B. Cook estimates that the meteor likely originated 60 miles above West Bend, Wisconsin, a small city 40 miles north of Milwaukee, reports Kenneth Chang at The New York Times. This monster could have been up to two feet across and weighed 600 pounds before it broke apart, Cook estimates. The fireball traveled northeast at 38,000 miles per hour before breaking to pieces 21 miles above Lake Michigan. The blast created low-frequency signals picked up as far away as Manitoba, and exploded with the force of ten tons of TNT.
One witness to the emerald fireball was Jim Dexter, a police officer on patrol in Lisle, Illinois, at the time. He caught the green streak on his dash cam, and shared the video, which was soon circulated by the National Weather Service. “It was too good not to share,” he tells Megan Crepeau, John Hector and Leonor Vivanco at The Chicago Tribune. “I thought about how few people actually saw it, but then there’s the amount of people I got to share it with.”
Philipp Heck, who curates meteors at Chicago’s Field Museum tells the Tribune team that this meteor was similar to one witnessed in 2003 over the Chicago suburb of Park Forest. That space rock dropped a shower of meteorites on several homes, including a six-pound chunk that crashed through the roof of a house in Olympia Hills. Overall, the public turned in 15 to 20 meteorites from the incident to the local police station.
Chang reports that it’s unlikely any remnants from the space rock that appeared Monday will ever be recovered if they fell into the big lake. Michael Hankey of the American Meteor Society tells Chang that around four meteors of similar size fall each year, but most go unnoticed, falling over areas with little population.
So why was the big streak green? Last tells Kennedy that the heat from the friction as the meteor moves through the atmosphere interacted with materials in the rock, producing the color. Certain compounds like nickel can cause meteors to produce shades of green.
There’s no way to predict when the next bright green meteor will appear, but there may be a slim chance to see something similar. This weekend, Comet 45P/Honda-Mrkos-Pajdusakova, a green comet discovered in 1948 is scheduled to appear in the morning sky and may be visible to the naked eye.