Do wet feet become impure by walking on dry urine whose substance has been removed but its ruling remains?

If your wet feet step on a dry impurity (najasa), they become impure. However, the dryness of the impurity does not mean that its substance has disappeared; rather, its substance remains. The Maliki jurists have explicitly stated that if the substance of an impurity (najasa) has disappeared, then whatever touches its place does not become impure, even if it is wet.