Every single day, many tons of tiny rocks—smaller than pebbles—hit the Earth’s atmosphere and disintegrate. Between frequent shooting stars we wish on in the night sky and the massive extinction-level asteroids that we hope we never see, there is a middle ground of rocks sized to make it through the atmosphere and do serious damage to a limited area. Now, new research from NASA indicates that the impacts of these mid-size rocks may be less frequent than previously thought.
Source:
https://phys.org/news/2019-06-tunguska-revisited-year-old-mystery-impact.html