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A fireball-shaped meteorite, which fell on a frozen lake and collected before being exposed to liquid water, gave an idea of what these rocks look like while still in space.
Researchers have found that it contains pristine organic compounds that could inform the origins of life on Earth.
On the night of January 16, 2018, a fireball meteor crossed the sky over the United States Midwest and Ontario before landing on a frozen lake in Michigan. The scientists used a weather radar to find out where the fragments landed, and meteor hunters were able to quickly collect them, before their chemical composition was changed by exposure to liquid water.
As they show in a new article in the journal Meteoritics & Planetary Science, which gave scientists an idea of what space rocks look like when they are still in space, including a look at pristine organic compounds that could tell us about the origins of life.
“This meteorite is special because it fell on a frozen lake and recovered quickly. It remained untouched and we could see that the minerals weren’t much altered and then we found that it contained a rich inventory of extraterrestrial organic compounds,” explains Philipp Heck , curator of the Field Museum, associate professor at the University of Chicago and lead author of the new article.
“These types of organic compounds were likely delivered to the early Earth by meteorites and may have contributed to the ingredients of life,” he adds.
Meteorites are space rocks that have fallen to Earth. When things like asteroids collide in space, the fragments can break off. These pieces of rock, called meteoroids, continue to float in space, and sometimes their new paths collide with moons or planets.
When a meteoroid crosses the Earth’s atmosphere and we can see it as a fireball or a shooting star, it is called a meteorite. If the parts of that meteor survive the journey through the atmosphere, the parts that actually land on Earth are called meteorites.
When the fireball reached Michigan, scientists used NASA’s weather radar to track where the pieces went. “The weather radar is meant to detect hail and rain,” explains Heck. “These meteorite pieces fell on that size range, so the weather radar helped show the meteorite’s location and speed. That meant we were able to find it very quickly.”
Less than two days after landing, meteor hunter Robert Ward found the first fragment on the frozen surface of Strawberry Lake, near Hamburg, Michigan. Ward worked with Terry Boudreaux to donate the meteorite to the Field Museum, where Heck and Jennika Greer, a graduate student at Field and University of Chicago and one of the authors of the article, began studying it.
“When the meteorite arrived at the Field Museum, I spent the entire weekend analyzing it, because I was so excited to know what kind of meteorite it was and what it was,” recalls Greer. “With every meteor that falls, there is a chance to let there be something completely new and totally unexpected.”
The researchers quickly determined that the meteorite was an H4 chondrite – only 4% of all meteorites falling to Earth these days are of this type. But what makes the Hamburg meteorite truly exceptional is how quickly it was collected and how well it is analyzed.
“This meteorite displays a great diversity of organic matter, because if anyone were interested in studying organic matter, this isn’t normally the type of meteorite they would ask to look at,” Greer said. “But because there was so much excitement in his running around, everyone wanted to apply their technique, so we have an unusually complete dataset for a single meteorite.”
Scientists aren’t sure how the organic (carbon-containing) compounds responsible for life on Earth got here, but one theory is that they got there in meteorites. This does not mean that the meteorites themselves contain extraterrestrial life, but rather that some of the organic compounds that help form life may have first formed in an asteroid that later fell to Earth.
“Scientists who study meteorites and space are sometimes asked if they ever see any signs of life. And I always answer that yes, all meteorites are full of life, but terrestrial, terrestrial life – says Heck -” As soon as it lands it becomes covered with microbes and life from the Earth. We have meteorites with lichens growing on them. So the fact that this meteor recovered so quickly after falling, and landed on ice in Instead of Something Contaminated, helped keep it cleaner. “
“This study is a demonstration of how we can work with specialists from around the world to get the most out of this little piece of raw, precious rock,” says Heck. “When a new meteor falls on a frozen lake, maybe even sometime this winter we’ll be ready. And next fall might be something we’ve never seen before.”
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