Earlier this year, the evening skies near Detroit (Michigan) lit up with bright flashes. These are not the only signs of meteor decay that fell on January 17, 2018. The meteor explosion was also recorded by infrasound microphones and seismometers, which makes it possible to compare this information with satellite and ground camera surveys.
The researchers use this data to calculate the time, location and height of the collapse of the car, as well as the calculation of the approximate damage from the explosion. Fireballs (“fireballs”) are extremely bright meteors that explode in the atmosphere. They are estimated at 0.8-8.1 tons of trotyl equivalent to 2.2 tons of trotyl.
Each year, 2000 fireballs of this size pass through the earth's atmosphere, which makes the Michigan case particularly interesting to study. Scientists wanted to learn more about how often we can expect to see similar near-earth objects in order to assess the potential threat to the Earth. Researchers use data from fireball bursts as “test cases,” which allows us to determine how well infrasonic and seismic instruments are able to find and characterize secret nuclear test explosions.
Other fireballs, like the February case in Chelyabinsk (Russia), 2013, were also intensively studied using infrasound, seismic and optical observations. A significant contribution was also made by casual witnesses who recorded what was happening on video. But this is an unusual event, which is expected every few decades. When the Michigan race car exploded and exploded in the lower earth's atmosphere, it created large shock waves and a variety of sound waves, including waves in the low-frequency or infrared destructive range below 20 hertz. Calculations on this information allowed us to determine the location, height, timing and coverage of the collapse of the car.
The analysis showed that infrasound and seismic calculations are consistent with optical observations, although some indicators, such as location and infrasound data, contained a large statistical uncertainty. But seismic indicators helped calculate the location and altitude in km.
Michigan's meteor is considered the smallest to detect CEUSN, so scientists are able to record about 15 events of this size. The analysis will allow researchers studying secret nuclear tests to draw conclusions on how to record events of this size and how far from the source of the explosion will be able to detect signals.
