They should have already done it! That means either the impact isn’t true, or aliens don’t exist.
Richard A. Posner 4, Circuit Judge on the United States Court of Appeals for the Seventh Circuit and Senior Lecturer at the University of Chicago Law School, LLB from Harvard University Law School, Catastrophe: Risk and Response, p. 31
The possible catastrophes examined by the assessors were not limited to a strangelet disaster. They included creating a black hole that would swallow the earth and maybe the rest of our solar system as well, and destroying the entire universe by causing a phase transition. What we call "space" may conceivably "exist in different 'phases,' rather as water can exist in three forms: ice, liquid, and steam. . . . Some [physicistsl have speculated that the concentrated energy created when [subatomic] particles crash together could trigger a 'phase transition' that would rip the fabric of space itself,'1 destroying all the atoms in the entire universe.48 However, these consequences seem much less likely even than a strangelet disaster. One minor though intriguing reason for thinking this is that if there is intelligent life elsewhere in the universe, as seems highly likely from the sheer number of planets (see the introduction), some civilization more advanced than our own would already have built a particle accelerator as powerful as RHIC, precipitating a phase transition that would have destroyed the universe.