"AIM will be watching closely as DART hits Didymoon," said ESA's Ian Carnelli, AIM mission manager. "In the aftermath, it will perform detailed before-and-after comparisons on the structure of the body itself, as well as its orbit, to characterize DART's kinetic impact and its consequences.
"The results will allow laboratory impact models to be calibrated on a large-scale basis, to fully understand how an asteroid would react to this kind of energy. This will shed light on the role the ejecta plume will play – a fundamental part in the energy transfer and under scientific debate for over two decades."
ANALYSIS: Nuking Asteroids: It's a Megaton Of Fun!
This will be the first time in human history that we've taken a vehicle, deliberately smashed it into a celestial body with the only intention of seeing how it reacts. The measurable results of the impact will be used to better prepare humanity should we be faced with the very real possibility of being hit by an asteroid that could cause regional, or even global, damage.
Understanding how an asteroid reacts to being hit is critical if we are to work out what we can possibly do to deflect hazardous space rocks in the future. Will they break apart on impact? Are they solid? Will the impactor just embed itself in a malleable rubble pile? Do we in fact need that nuclear warhead? In short, we're not entirely sure.
In 2005, NASA's Deep Impact mission collided a dense copper impactor into the nucleus of comet Tempel 1. However, this attempt wasn't to deflect the comet, it was to study the impact ejecta; the kinetic energy imparted on the comet was negligible.
Didymoon, however, is several tens of times smaller than Tempel 1, so the DART impact will have a small, yet highly significant effect on the asteroid's trajectory.
The Didymos binary will come within 11 million kilometers (nearly 30 times the Earth-moon distance) of Earth in 2022 (the point of closest approach with our planet), so it will be well out of harm's way as the DART impact takes place.
ANALYSIS: Don't Be Subtle, Nuke That Asteroid
Interestingly, Didymoon is nearly three times larger than the estimated size of the Tunguska impactor that leveled 80 million trees over a 2,150 square kilometer (830 square mile) region of Siberia in 1908. If an asteroid the size of Didymoon hit Earth, it would be classed as a "city killer", ripping out a crater 2.5 kilometers wide, causing wide-spread devastation. As a modern comparison, the meteor that exploded over Chelyabinsk, Russia, in 2013 was a mere 20 meters wide - nearly 9 times smaller than Didymoon.