Kinetic impactors are the simplest solution within our reach.
Earth and Planetary Science Letters.
Iridium is an element that is rare on Earth but relatively abundant in many.
If the asteroid is large enough, these could be global in impact.
In the late 20th and early 21st century scientists put in place measures to detect , and predict the dates and times of impacting Earth, along with the locations at which they will impact.
On its way to the impact, the asteroid pushes aside the air in front of it creating a hole in the atmosphere.
It is now thought to be a remnant of the mission in 1998, and is the third time any previously unknown object — natural or artificial — was identified prior to impact.
By 29 April 2019, the first day of the Planetary Defence Conference , the probability of impact has risen to 1 in 100.