This experiment will determine how the structure and porosity of Amorphous Solid Water (ASW) changes when the “ice” is “contaminated” by adsorbate molecules. ASW is a porous material formed by vapour-depositing water onto a cold plate, an analogue of the ice found in star- and planet-forming regions of our galaxy. Our previous work has shown that the ASW has very small-scale porosity, but NIMROD data of the pure water ice alone are unable to elucidate pore accessibility; open pores can trap volatile molecules well beyond their desorption temperature and therefore act as a reservoir for coolant molecules in star-forming regions. This experiment tests ASW porosity evolution as a function of ice-adsorbate morphology and measures ASW structural changes as the ice is grown and heated, exploiting the broad Q-range of NIMROD to probe the molecular level and meso-scale of the ice concurrently.