What is the smallest asteroid known and how much could it destroy, like a city, island, continent etc (for Powerscaling)
The smallest known asteroid is likely a few meters in diameter. Asteroids of this size are known as meteoroids when they are in space and become meteors when they enter the Earth's atmosphere and burn up. Typically, these small meteoroids do not reach the Earth's surface and pose no significant threat.
If we consider a slightly larger asteroid, approximately 20 meters in diameter, it could cause localized damage if it were to impact the Earth's surface. This size range is similar to the Chelyabinsk meteor that exploded over Russia in 2013. The energy released by that explosion was estimated to be equivalent to about 400 to 500 kilotons of TNT—roughly 20 to 25 times the energy of the atomic bomb dropped on Hiroshima. This event caused damage to buildings, shattered windows, and resulted in injuries to people due to the shockwave. However, it did not cause widespread destruction or pose a major threat to a city or larger area.
When it comes to impacting cities, islands, or continents, we need to consider significantly larger asteroids. For example, the asteroid that is believed to have caused the extinction of the dinosaurs, known as the Chicxulub impactor, is estimated to have been about 10 kilometers (6 miles) in diameter. It created a global catastrophe, triggering massive wildfires, tsunamis, and sending an enormous amount of debris into the atmosphere, resulting in long-term climate changes. Such large impacts have the potential to cause widespread devastation, leading to significant loss of life and affecting entire ecosystems.
It's important to note that the potential damage caused by an asteroid depends on various factors such as its size, composition, speed, angle of entry, and location of impact. Scientists closely study and track asteroids to understand these properties and assess any potential threat they may pose to our planet.