The “ fireball ” meteorite that fell to Earth in 2018 reveals its secrets


A fireball meteor was seen darting through the sky over the Midwest and Ontario on the evening of January 16, 2018. Meteorological data helped scientists quickly track where the pieces of the meteor fell on Earth so they could be collected earlier. that the samples from space were too contaminated by Earth.

“Weather radar is meant to detect hail and rain,” study lead author Philipp Heck, curator of the Chicago Field Museum and associate professor at the University of Chicago, said in a statement. “These meteorite pieces fell in that size range, and so the weather radar helped show the meteorite’s position and speed. That meant we were able to find it very quickly.”

Elements on Earth, including liquid water, can change the chemical composition of a meteorite before it is even collected.

But the Hamburg meteorite – collected less than two days after falling to Earth – is a prime example of a largely unaffected meteorite.

Meteorite hunter Robert Ward found the first piece of the meteorite on the frozen surface of Strawberry Lake, near Hamburg, Michigan. Ward and private collector Terry Boudreaux donated the meteorite to the Field Museum so it could be studied.

Meteorite hunter Robert Ward is pictured with the meteorite on Strawberry Lake near Hamburg, Michigan.

“This meteorite is special because it fell on a frozen lake and was recovered quickly. It was very pristine. We could see that the minerals weren’t much altered and we later found that it contained a rich inventory of extraterrestrial organic compounds,” he said. Heck. “These types of organic compounds were likely delivered to early Earth by meteorites and may have contributed to the ingredients of life.”

The study was published Tuesday in the journal Meteoritics & Planetary Science.

“When the meteorite arrived in the field, I spent the whole weekend analyzing it, because I was so excited to find out what kind of meteorite it was and what it contained,” said Jennika Greer, co-author of the study and PhD student at the Field. and the University of Chicago, in a statement.

“With every meteor that falls, there is a possibility that there is something completely new and totally unexpected.”

Here’s what they learned.

Souvenirs from space

The Hamburg meteorite is largely untouched because it was collected so quickly after falling to Earth. This means that the meteorite has not stood still long enough to be exposed to the elements, for its metals to begin to rust, for water to seep through the cracks and contaminate it, or for its minerals (such as olivine) to be altered. .

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This rapid recovery of the meteorite makes it “remarkable,” Heck told CNN in an email. And the buzz around the meteorite led to it being well studied and analyzed by researchers from 24 different institutions.

Scientists believe the Hamburg meteorite was ejected from its parent asteroid about 12 million years ago, traveling in space until it landed on Earth. An analysis of the meteorite revealed that the rock had been exposed to cosmic rays as it sped through space for 12 million years.

The meteorite fragment that fell on Strawberry Lake includes pristine organic compounds.

The meteorite came from an asteroid that formed 4.5 billion years ago, only about 20 million years after the formation of our solar system, Heck said.

The 2,600 different organic compounds that cover the Hamburg meteorite were formed in his parent asteroid.

It is what is known as H4 chondrite, a type of meteorite that is not known to be rich in organics.

“This meteorite exhibits a high diversity of organics, as if anyone were interested in studying organics, this is not normally the type of meteor they would ask to look at,” Greer said. “But because there was so much excitement surrounding it, everyone wanted to apply their technique to it, so we have an unusually complete dataset for a single meteorite.”

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Typically, carbonaceous chondrites are a thousand times richer in organics than H4 chondrites, Heck said. The near-Earth asteroid Bennu, which was recently sampled by NASA’s OSIRIS-REx mission, is rich in carbon.

“The fact that this ordinary chondrite meteorite was rich in organics lends support to the hypothesis that meteorites played an important role in delivering organic compounds to the early Earth,” Heck said. “Meteorites fell on our planet over the course of Earth’s history even before life was formed and possibly brought some of the building blocks to life on Earth.”

The organic matter in the meteorite was originally once heated up to 1,200 degrees Fahrenheit while it was still part of its parent asteroid. This effectively reduced the diversity of organic compounds in the meteorite from millions to a couple of thousand. But Heck was still amazed at how many organic compounds were still in the meteorite despite the heat-induced changes it underwent.

The asteroid Bennu has been around with Earth for over a million years

Researchers found hydrocarbons and compounds containing sulfur and nitrogen.

“Much more work needs to be done to better understand the individual chemical pathways of different compounds and the different processes that organic matter has gone through,” Heck said.

The Hamburg meteorite can be compared with other samples collected in the future, including pristine samples returned from asteroids by the Japanese Aerospace Exploration Agency’s Hayabusa2 mission and NASA’s OSIRIS-REx mission. The first sample of the asteroid Ryugu will be delivered to Earth by Hayabusa2 in December, while the Bennu sample will return in 2023.

“But we also keep looking for new meteor falls,” Heck said. “Every meteor that falls on Earth deserves to be studied, as it can provide a unique perspective on the solar system and can shed new light on its history and our origins.”


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