First, it has been shown that moisture is more prevalent in deserts than first thought and may be the driving mechanism in rock fracturing. Secondly, laboratory experiments in which rocks have been subject to simulated desert conditions have failed to confirm field observations. Fourthly, many weathering features attributed to insolation, such as exfoliation, have been found at depth far removed from the influence of diurnal variations. So clearly, the jury is still out on insolation weathering. Although desert environments are dry, few areas are hyper-arid and most receive moisture in a wide variety of forms.
Moisture is important in several regards.
First, virtually all minerals are soluble to some extent in natural waters. Secondly, moisture promotes biological growth, which in turn can breakdown rock through, for example, root action. Rock fracturing through root action enables moisture to penetrate to depth allowing other weathering processes to take place. Thirdly, many desert environments are alkaline due to the presence of salts. In some case, lake pH levels exceed 10.