article_snippet.sent: It is an astronomical nightmare - if an asteroid were spotted headed towards Earth, what could humanity do about  ?
article_snippet.sent: An artist's impression of what could happen when Craft hits the asteroid.
article_snippet.sent: Experts hope the impact will be large enough to alter the impact orbit.
article_snippet.sent: A similar collision was achieved back in 2005, when NASA's Deep Impact spacecraft shot a copper impactor into asteroid Tempel 1.
article_snippet.sent: But the moon is several tens of times smaller than Tempel 1, so much greater precision will be required to strike the moon – and the possibility of altering the moon orbit should be correspondingly higher.
article_snippet.sent: the moon is nearly three times larger than the body thought to have caused the 1908 Tunguska impact in Siberia, the largest impact in recorded history.
article_snippet.sent: An equivalent asteroid striking Earth would be well into the 'city-killer' class, leaving a crater of at least 2.5 km across and causing serious regional and climate damage.
article_snippet.sent: The 2013 Chelyabinsk airburst, whose shockwave struck six cities across Russia, is thought to have been caused by an asteroid just 20 m in diameter.
article_snippet.sent: In the aftermath, the mission for ESA will perform detailed before-and-after comparisons on the structure of the body itself, as well as as well orbit, to characterise DART's kinetic impact and as well consequences.
article_snippet.sent: 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. '
article_snippet.sent: 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. '
article_snippet.sent: We will gain insight into the kind of force needed to shift the orbit of any incoming asteroid, and better understand how the technique could be applied if a real threat were to occur.'
highlights_snippet.sent: Craft will watch as Nasa sends a probe crashing into the asteroid's surface .