I have seen two answers to why surfaces 'wring', ie stick together when below a specific level of roughness. This includes two general answers. The first is that they are acting like a suction cup, and therefore the force holding the objects together is the surrounding atmospheric pressure. The other answer though I have heard is that once the atoms get that close together across the entire surface, a bonding between the surfaces happen because of the attraction of the atoms to each other.
These answers seem very different, and yet I hear both anytime the question is brought up. Is there any testing that has been done of the the 'wringing' effect in a vacuum to know if there is an attractive force because of the atoms, that has nothing to do with the atmospheric pressure, and thus the effect would also occur in space for example? Or perhaps is both things going on, and combining for a larger effect say then either by themselves?