That is one big rock, one big shift in our relationship with space. The first attempt by humans to interfere in the dance of the solar system will be made on Wednesday. The aim is to test drive a planetary defence system that could prevent us from going the same way as the dinosaurs.
Our planet is bombarded with small pieces of debris, but they are usually burned or broken up before they hit the ground. Something large enough to do significant damage hits the ground occasionally. The dinosaurs were thought to have died off 66 million years ago, when a collision ejected huge amounts of dust and debris into the upper atmosphere, which obscured the sun and caused food chains to collapse. Someday, something similar could call time on humanity's reign, unless we can find a way to distract it.
The Double Asteroid Redirection Test (Dart) mission is the first attempt to test if the strategy of intentionally colliding with an asteroid is realistic.
Jay Tate, the director of the National Near Earth Objects Information Centre in Knighton in Wales, said that this is the first step to trial a way of preventing near-Earth object impact. It would be a big deal if it works, because it would show that we have the technical ability to protect ourselves.
The Dart is scheduled to blast off from the Vandenberg Space Force Base in California on Wednesday at about 6.21am UK time. The Didymos system consists of a pair of harmless asteroids, called Dimorphos and Didymos, that are in close proximity to each other.
Occasionally, these asteroids pass close to Earth. The plan is to crash the spaceship into Dimorphos when the asteroid system is at its closest point.
A miniaturised satellite called the Light Italian CubeSat will separate from the main satellite about 10 days before the impact. Scientists can calculate the degree to which the impact has altered Dimorphos's path with the help of recordings from ground-based telescopes and an onboard camera.
The expectation is that it will change the speed of the smaller asteroid by a fraction of 1% and alter its orbital period around the larger asteroid by several minutes.
The European Space Agency will visit the Didymos system and conduct a further analysis of the consequences of the snooker game in November of 2024. If an apocalyptic asteroid were to ever be detected, the details of this technique would be vital.
It is unlikely that any single strategy would be enough. Tate said that the mission will provide real time ground truths on the effects of a small impactor on a small asteroid. The problem is that no two asteroids or comets are the same, and how you divert one depends on a lot of variables.
There is no silver bullet in this game. You need a folder of different methods for different types of target.
This may be a small step towards planetary protection, but many more are needed to avoid Armageddon.