A meteorite that landed on a frozen lake in 2018 contains thousands of organic compounds that formed billions of years ago and will hold clues about the origins of life on Earth.
The meteor entered Earth's atmosphere on Jan. 16, 2018, after an awfully long journey through the freezing vacuum of space, lighting up skies over Ontario, Canada, and also the midwestern us.
Weather radar tracked the flaming space rock's descent and breakup, helping meteorite hunters to quickly locate fallen fragments on Strawberry Lake in Hamburg, Michigan.
An international team of researchers then examined a walnut-size piece of the meteorite "while it had been still fresh," scientists reported in a very new study. Their analysis revealed over 2,000 organic molecules dating to when our system was young; similar compounds may have seeded the emergence of microbial life on our planet, the study authors reported.
A meteorite found on a frozen Michigan lake. (Field Museum)
Swift recovery of the meteorite from the lake's frozen surface prevented liquid water from seeping into cracks and contaminating the sample with terrestrial spores and microbes. This maintained the space rock's pristine state, enabling experts to more easily evaluate its composition.
In fact, there was so little terrestrial weathering that the fragment delivered to Chicago's Field Museum gave the look of it had been collected in space, said study co-author Jennika Greer, a doctoral candidate within the Department of the Geophysical Sciences at the University of Chicago, and a resident postgraduate at the sector Museum.
When space rocks enter the atmosphere at speeds of several miles per second, the air around them becomes ionized. Extreme heat melts away up to 90 percent of the meteor, and also the rock that survives atmospheric passage becomes encased in an exceedingly 1-millimeter-thick fusion crust of melted glass, said lead study author Philipp Heck, a curator of meteorites at the sphere Museum and a prof at the University of Chicago.
That surviving fragment inside the glassy crust may be a pristine record of the rock's geochemistry in space. And despite a fiery fall to Earth, after the vaporized external layers are frenzied, rocky meteorites like this one are very, very cold once they land, Heck told Live Science.
"I've heard eyewitness accounts of meteorites falling into puddles after it rained, and also the puddle froze because the meteorite was so cold," he said.
Mostly unchanged
The Michigan meteorite's ratio of uranium (isotopes 238 and 235) to the element's decayed state as lead (isotopes 207 and 206) told the scientists that the parent asteroid formed about 4.5 billion years ago.
Around that point, the rock underwent a process called thermal metamorphism, because it was subjected to temperatures of up to 1,300 degrees Fahrenheit (700 degrees Celsius). After that, the asteroid's composition stayed mostly unchanged for the last 3 billion years.
Then about 12 million years ago, an impression broke off the chunk of rock that recently fell in Michigan, in line with an analysis of the meteorite's exposure to cosmic rays in space, Heck told Live Science.
Frame from security video of the Hamburg fireball. (T. Masterson/American Meteor Society)
Because the meteorite was altered so little after its initial heating billions of years ago, it absolutely was classified as H4: "H" indicates that it is a rocky meteorite that's high in iron, while type 4 meteorites have undergone thermal metamorphism sufficient to vary their original composition.
Only about 4 percent of the meteorites that fall to Earth today land within the H4 category.
"When we're watching these meteorites, we're watching something that's near the fabric when it formed early within the Solar System's history," Greer said.
The meteorite held 2,600 organics, or carbon-containing compounds, the researchers reported within the study. Because the meteorite was mostly unchanged since 4.5 billion years ago, these compounds likely are just like those that other meteorites dropped at a young Earth, a number of which "might are incorporated into life," Heck said.
The transformation from extraterrestrial organic compounds into the primary microbial life on Earth is "a big step" that's still shrouded in mystery, but evidence suggests that organics are common in meteorites – even in thermally metamorphosed meteorites like the one that landed in Michigan, he added.
Meteor bombardment was also more frequent for a young Earth than it's today, "so we are pretty certain that the input from meteorites into the organic inventory on Earth was important," for seeding life, Heck said.
The findings were published online Oct. 27 within the journal Meteoritics & Planetary Science.
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