WASHINGTON-In January 2018, a falling meteorite created a bright fireball that arced over the outskirts of Detroit, Michigan, followed by loud sonic booms.

The visitor not only dropped a slew of meteorites over the snow-covered ground, it also provided information about its extra-terrestrial source.

Although tens of thousands of meteorites have been recovered by humans, scientists have only been able to trace the orbits of a small number. Most of these have been calculated in the last decade.

Scientists can use information about how the meteorite burned through Earth’s atmosphere to calculate how the rocky object moved through space before it transformed into a fireball.

Researchers cannot trace the specific path of an object back through time - there are too many variables that could have affected its motion. But they can determine the most likely paths. Studying the likely orbits of similar asteroids can help to reveal their parent body, the larger asteroid they once were part of.

“This is a great way to do what amounts to a low-cost asteroid sample return mission,” says Dr Peter Brown, who studies asteroids at Canada’s University of Western Ontario. “In this case, the sample comes to us. We don’t have to go to the sample.”

Dr Brown and his colleagues gathered information from fireball surveys as well as videos posted on social media to reconstruct a potential orbit for the Hamburg meteorite, named after the small Detroit suburb it buzzed.

The team then worked with several of the amateur photographers to calibrate their observations. “We spent a lot of time scouring YouTube and Twitter,” he says.

The researchers found that the Hamburg meteorite was a fairly typical fireball. It likely entered the atmosphere with a mass ranging from 60kg to 220kg and a diameter between 0.3m and 0.5m.

Travelling at about 16 km/s, it produced two major flares at 24.1km and 21.7km above the ground. The total energy produced by the fireball equalled somewhere between two and seven tonnes of TNT.

While some researchers took to the ground to hunt for dark meteorites in the Michigan snow, Dr Brown and his colleagues took to the internet to find reports of the fall. Because the region was densely populated, Dr Brown said there were a lot of video recordings that captured the fall.

Out of the wealth of camera phone and security footage, they tracked down almost 30 unique videos that were sharp enough to reveal their location. Of these, only a handful was good enough for the team members to perform detailed calibration.

How do you calibrate a casual fireball video? First you need to have a positional reference that helps to pinpoint where the video was taken from. Ideally, the same camera would be placed in the exact spot where the meteorite fall was originally viewed - though often a similar camera was used instead.