Those charges also had plenty of gas bubbles. Even the samples heated in vacuum, where escape of the gas should have been easier, contain significant percentages of gas bubbles. Scanning electron microscope image of a typical experimental charge. This one was flash heated at 1500 o C for 5 seconds and quenched in a few seconds. The dark areas with straight sides are crystals of olivine that formed during the rapid cooling of the experimental charge.
Bright material is glass.
The table below summarizes the results of the experiments. This tells us that the events that melted the dust aggregates must have taken place before any hydrated minerals formed, implying formation before the temperature dropped to about 400 K in the vast cloud of gas and dust from which the Solar System formed. Instead, it may have condensed as ice. If an aggregate of ice and water-free minerals is flash heated, gas bubbles will also be produced. No experiments on mineral-ice powders have been done.