What if you 'placed' the Chicxulub asteroid onto the Earth?
An asteroid resting on Earth would be a mountain. Or, for smaller asteroids, a pile of gravel.
Mountains are limited in altitude by the strength of stone to resist compression: a too tall mountain would sink down as the base crumbled and spread out. The limit on Earth is about 10 km. Besides the strength issue mountains are also floating (&quot;isostasy&quot;) on the fluid but denser interior of Earth, so even if it doesn't fall apart it may sink down partially.
So the impactor would not hold together that well. A big ball of rock 10 km in diameter would first definitely sink down several kilometres into the crust, and almost definitely break. That means that something like $10^{15}$ kg will descend several kilometres, giving an energy $mgh \approx 10^{19}$ J (and there are estimates 100 times larger for the mass). That is &quot;just&quot; like a big hurricane, but will mostly be released as localized seismic energy and heating. The end result would be a massive pile that likely destabilizes the crust in the vicinity a lot: far less than an actual high velocity impact, but still a major disaster.
If you do the same with the moon you will break up the crust, boil off the oceans and wipe out all life on the planet.