An international team of researchers has found extraterrestrial hydrocarbons, sulfurized and nitrogen-containing compounds in the Hamburg meteorite, which landed on frozen lakes in Michigan in 2018.
The Hamburg meteorite fell on January 16, 2018, near Hamburg, Michigan, after a fireball event observed and reported by 674 witnesses from 10 U.S. states (Michigan, Illinois, Wisconsin, Ohio, Pennsylvania, Indiana, West Virginia, Georgia, Missouri, and Kentucky) and Ontario, Canada.
The atmospheric shockwave was registered by several infrasound sensors in the Central and Eastern United States and six seismometer stations as the equivalent of a 1.8-magnitude earthquake. Footage of the fireball was acquired by multiple security cameras.
Several fragments of the space rock fell onto frozen surfaces of lakes and, thanks to weather radar data, about 1 kg of fragments were recovered. Radar reflections suggested a total surviving mass of only 2 kg.
“This meteorite is special because it fell onto a frozen lake and was recovered quickly,” said Dr. Philipp Heck, a curator at the Field Museum and a researcher at the University of Chicago.
“It was very pristine. We could see the minerals weren’t much altered and later found that it contained a rich inventory of extraterrestrial organic compounds.”
“These kinds of organic compounds were likely delivered to the early Earth by meteorites and might have contributed to the ingredients of life.”
Less than two days after the Hamburg meteorite landed, meteorite hunter Robert Ward found the first piece of the meteorite on the frozen surface of Strawberry Lake, near Hamburg, Michigan.
Ward worked with Terry Boudreaux to donate the meteorite to the Field Museum, where the scientists began to study it.
“When the meteorite arrived at the Field Museum, I spent the entire weekend analyzing it, because I was so excited to find out what kind of meteorite it was and what was in it,” said Jennika Greer, a graduate student at the Field Museum and the University of Chicago.
“With every meteorite that falls, there’s a chance that there’s something completely new and totally unexpected.”
The researchers determined that the Hamburg meteorite is an H4 chondrite — only 4% of all meteorites falling to Earth these days are of this type.
They also found that the fragments fell from a 40-60 cm sized meteoroid with a total mass of 50 kg.
“This meteorite shows a high diversity of organics, in that if somebody was interested in studying organics, this is not normally the type of meteorite that they would ask to look at,” Greer said.
“But because there was so much excitement surrounding it, everybody wanted to apply their own technique to it, so we have an unusually comprehensive set of data for a single meteorite.”
“You learn a lot more about a meteorite when you sample different pieces,” she added.
“It’s like if you had a supreme pizza, if you only looked at one little section, you might think it was just pepperoni, but there might be mushrooms or peppers somewhere else.”
“This study is a demonstration of how we can work with specialists around the world to get most out of the small piece of raw, precious piece of rock,” Dr. Heck said.
“When a new meteorite falls onto a frozen lake, maybe even sometime this winter, we’ll be ready. And that next fall might be something we have never seen before.”
The study was published in the journal Meteoritics Planetary Science.
Philipp R. Heck et al. The fall, recovery, classification, and initial characterization of the Hamburg, Michigan H4 chondrite. Meteoritics Planetary Science, published online October 27, 2020; doi: 10.1111/maps.13584