The timing could not have been better.
A week after the Field Museum unveiled its new interactive meteorite display, a green fireball went streaking across the night sky above Illinois, Wisconsin and part of Iowa, as seen captured on a number of squad car dashcams.
Well, maybe a little better.
“One could hit the Field Museum,” mused Philipp R. Heck, a little wistfully. “A small one. Then it could be the Field Meteorite.”
Heck is the museum’s Robert A. Pritzker associate curator of meteorites and polar studies. If you’re wondering about the connection between rocks from the sky and global ice caps, ponder the challenge of trying to find the meteorite that fell to Earth on Monday morning. It landed in a spray of debris in Lake Michigan, about five miles east of Sheboygan.
“If the lake were frozen, I might be out there right now looking for it,” said Heck, holding a satellite photo map he received that morning from NASA showing the meteorite’s “strewn field,” the area where pieces might fall. A region of maybe 50 square miles where you would have to comb the lake bottom, 150 feet down, looking for rocks the size of peanuts.
Or you could go to the South Pole — as Heck has, helping the Indian government develop its meteorite research program — where the shifting glacial ice has a way of consolidating meteorites and offering them up.
“They become part of the glacier,” said Heck. “Because of the wind and solar radiation, the ice disappears and everything in the ice just pops to the surface. . . . Besides meteorites, there’s not much that pops up.”
Meteorites (as they’re called when they hit Earth; beforehand they’re “meteors”) are keyholes into time and space. You can’t go to the asteroid belt between Mars and Jupiter, but the asteroid belt can come here, in the form of meteors projected into our direction by collisions there. Of particular interest to Heck is an enormous collision that happened 466 million years ago, which showered the Earth with debris. The problem of finding rocks that old is their minerals disappear, but Heck was able to locate minute fossilized meteorite fragments — tiny slivers of ancient stone that became fossilized over time, just like bones of dinosaurs. He published a paper on that topic last month in Nature Astronomy.
“They provide us a window into the past,” Heck said. “They recall events from very early on and preserve them as a mineral record. We learn how the solar system formed. We don’t find old rocks like this on Earth.”
Our planet is 4.5 billion years old, but the oldest rocks on it are 3.8 billion years old. Meteorites, on the other hand, can be 4.6 billion years old.
Meteorites do have their mundane aspects. Steve Zitowksy is a volunteer at the Field. On Tuesday he unpacked a box containing a large round stone shipped from Kansas. If you think you’ve found a meteorite, the Field will analyze it. But before you start gathering the stones from your koi pond to mail in, bear this in mind: they’re not meteorites. Almost certainly. “We call them ‘meteorwrongs,'” said Zitowsky. Sites of old steel mills are a particularly rich source of amateur “finds.”
“Slag looks a lot like meteorites at first blush,” he said.
The Field’s collection started with 170 meteorites gathered for the 1893 World’s Fair. Now it has 2,970 specimens from 1,600 different meteorites, mostly housed in 33 metal lockers containing wooden drawers labeled with the place of origin, “Canyon Diablo” and “Cape York” and such. Three are labeled “Loans & Gifts” of Terry Boudreaux, the Lake Forest meteorite collector and museum patron.
The new exhibit is small, a few display cases on the second floor, tucked nearby the Hall of Jade. But it has a model of a meteorite that the Mars rover Opportunity discovered on the surface of Mars. It scanned the rock, and technicians at the Field reproduced it so you can run your hands over the twin of a meteorite that is still sitting on the surface of Mars. Which is kinda cool.Tweets by @neilsteinberg