On Jan. 16 around 8:10 p.m. local time, a brilliant, green fireball sliced across the skies of southern Michigan near Ann Arbor. Many eyewitnesses said it looked as bright as a full moon. The American Meteor Society, a clearinghouse for meteor sightings, has received about 640 reports so far from people who saw the object from as far away as Iowa and southern Ontario.
The meteor moved relatively slowly, “only” about 28,000 miles per hour (45,000 km/hour). That sounds fast but it’s more than 4½ times slower than a typical meteor in the summertime Perseid shower. Its slow speed and great brilliance suggests a fairly large space rock that penetrated deep into the atmosphere, according to Mike Hankey of the AMS. At least 77 observers reported explosive sounds as it broke apart.
Although the meteor was visible across hundreds of miles, the actual fall occurred just south of Hamburg, Michigan about 20 miles northwest of Ann Arbor. The strewn field, the name for the ground footprint where the space rocks fell, extends about 5 miles, oriented east-southeast to west-northwest, from about Highway 23 up to Bass Lake.
Videos of the Michigan fireball
Anyone living in that area should be on the lookout for black rocks poking out of the snow similar to what Ward is holding in the photograph. The black color, called fusion crust, forms when the outside of the meteoroid is heated and melted from friction during its flight through the atmosphere. Fusion crust is typically only 1-2 mm thick.
More cool videos of the fireball
I still haven’t heard what kind of meteorites fell, whether rare or common. But I can tell you that it’s rare enough for any meteorites to be recovered from a any fireball. For this and other recent meteorite finds, Doppler weather radar traces were used to estimate the location of the strewn field.
The Michigan fireball announced its arrival in another way via a 2.0 magnitude seismic event recorded by the U.S. Geological Survey. NOT from the impact itself but from the pressure wave created during the explosive breakup of the object.
A preliminary analysis indicates it’s possibly an L6 chondrite, a common stony meteorite type. The “L” stands for low iron and “6” (on a scale from 3 to 7 from least to most altered by heat) indicates that the meteorite was strongly heated, so it likely came from a larger asteroid. Samples are on their way now to the Chicago Field Museum for more detailed analysis and classification.