Mifflin Meteorite finds permanent home in Geology Museum

The meteorite that lit up the skies over southwest Wisconsin this spring has been officially dubbed the “Mifflin Meteorite,” and several of its pieces are now part of the permanent collection of the University of Wisconsin–Madison Geology Museum.

Though its dramatic fall did spark a frenzy of activity, no, it wasn’t named after the block party.

Instead it is named after Mifflin Township, near the center of the area in southwest Wisconsin showered by the meteorite on Apr. 14, 2010. The name was officially approved in late August by the Meteoritical Society, an international organization devoted to the study of objects from space.

While the new name reflects where the meteorite landed, scientific analyses are revealing where it came from. Noriko Kita, a meteorite expert at UW–Madison, led a team of researchers from UW–Madison, the Field Museum, the University of Chicago, and the Smithsonian Institution that analyzed the chemical composition, oxygen isotope ratio, and structure of the rock.

They classified the meteorite as an “ordinary chondrite subgroup L5” based on its composition and high degree of metamorphism, which indicate its origin from the interior of an asteroid formed 4.6 billion years ago.

As with most other meteorites, a parent asteroid of the Mifflin meteorite originated in the asteroid belt located between Mars and Jupiter. Gravitational interaction with the giant planet Jupiter can disturb asteroid orbits and cause collisions with other asteroids. Some fragments from these collisions end up having elliptic orbits that can cross Earth’s orbit and land as meteorites.

“There are a lot of L chondrites that have been found on Earth, and it’s thought that they all came from the same asteroid,” says John Valley, a UW–Madison professor of geoscience.

About 470 million years ago, the Earth was pummeled with debris, all with the same chemical signature, he says. Though the activity tapered off over the next 10 million years, occasional meteorites still hit the Earth.

“The hypothesis is that there was a collision, probably in the asteroid belt, that a fairly good-sized asteroid broke up and threw debris into the inner solar system. A lot of it hit the Earth, but there are still bits and pieces of it orbiting as asteroids even today,” Valley says. “We think that the April 14th meteorite was one more stone from that break-up.”

Eight pieces of the Mifflin Meteorite are currently on display in the UW Geology Museum. Five are on loan to the museum, four from local veterinarian Chris Pagel and one from an anonymous landowner. Three are now part of the museum’s permanent collection, acquired with help from Shea Gorzelanczyk of Green Bay and the Friends of the Geology Museum.

The largest piece on display weighs 142 grams and is roughly the size of a racquetball. Another piece, referred to as an oriented nose-cone, resembles a human nose and shows the orientation it had as it entered the atmosphere. All of the fragments on display show the black fusion crust that formed as the meteorite passed through the Earth’s atmosphere.

The Mifflin fragments are part of an exhibit featuring six of the 14 meteorites known to have landed in Wisconsin.

The UW Geology Museum is free and open to the public 8:30 a.m.-4:30 p.m. Monday-Friday and 9 a.m.-1 p.m. Saturday. The museum will be closed on Thursday, Nov. 25, and Friday, Nov. 26, but will resume normal hours on Saturday, Nov. 27.

The Geology Museum is also holding a holiday sale on Friday, Dec. 3, and Saturday, Dec. 4, from 10 a.m.-4 p.m. both days. There will be unique gifts for the rock hound on your list, including Spinosaurus tooth replicas, Megalodon shark teeth, ulexite (TV rock), giant pyrite specimens and much more.