Dashcam video of the meteor courtesy of the Lisle Police Department
A bright green fireball fell from the sky into Lake Michigan early Monday morning. Such events were not unknown in ancient mythologies when the gods were displeased, but scientists at the Field Museum and the American Meteor Society have assured us that it was just a meteorite breaking into pieces as it entered the earth's atmosphere. The technical term for it, though, is a "sporadic fireball," which is still pretty awesome.
Philipp Heck, the Field Museum's curator of meteoritics, says this is the largest meteorite to have landed in the Chicago area since the Park Forest meteorite of March 2003. That one had a mass of about 30 kilograms; radar analyses performed by Marc Fries, a research scientist at NASA, seem to indicate that the meteorite that hit on Monday was a similar size.
Scientists at the AMS have been busy calculating the meteor's trajectory, based on eyewitness accounts. It appears that it first emerged about 40 miles north of Milwaukee and streaked northeast, decelerating as it passed through lower, denser levels of the atmosphere, before crashing into the lake just east of Manitowoc. "We are discussing options of how to best retrieve fragments from the bottom of the lake," Heck writes in an e-mail. "No recovery efforts are currently underway. We finally have a good idea of the strewnfield, a map of where most likely fragments could be found."
Heck won't know for sure what sort of body the meteoroid broke off from, but, he writes, "The fireball size and behavior, the radar echo from the falling meteorites that was picked up by the radar was all similar to the Park Forest meteorite fall from 2003. I think the meteorites were therefore most likely from a rocky asteroid."
Unlike many meteorites, this one also made noise as it fell. Paul Mayer, the Field's collection manager of fossil invertebrates, was in Freedonia, Wisconsin, at the southwest end of the meteorite's trajectory, when it passed over. "I . . . was woken up by a large boom that shook the whole house," he writes. "It sounded like thunder and I thought maybe it was a train hitting something. I got up and looked out the window, but did not see anything. It was not until the next day when I saw the news that I realized it must have been the meteorite.”
(A fun fact from the AMS meteorite FAQ page
: "Those with a large amount of hair seem to have a better chance of hearing these sounds.")
The AMS estimates that several thousand fireballs fall every day, but most of them fall in daylight or over oceans and other uninhabited areas. Sporadic fireballs are said to appear three or four times a year. Heck would not comment as to whether there have been more occurrences in recent times. "It depends how long people look at the sky," he says.