While contributions from all three of these factors are usually in effect when ice skating, the scientific community has long debated over which is the dominating mechanism. For several decades it was common to explain the low friction of the skates on ice by pressure melting, but there are several recent arguments that contradict this hypothesis. The strongest argument against pressure melting is that ice skating is still possible below temperatures under -20 °C (253K). At this temperature, a great deal of pressure (>100MPa) is required to induce melting. Just below -23 °C (250K), increasing the pressure can only form a different solid structure of ice (Ice III) since the isotherm no longer passes through the liquid phase on the phase diagram. While impurities in the ice will suppress the melting temperature, many materials scientists agree that pressure melting is not the dominate mechanism.