Wadi Lawayni is a remote desert valley in the interior Al-Hajar Mountains of Oman, east of Saudi Arabia. A visitor gets there by following a lonely dirt road that dwindles to tire tracks running through a gravelly wash. Groundwater in this region occasionally surfaces in small pools that have a bluish tint—saturated with alkaline salts and sometimes so full of hydrogen gas that the liquid fizzes like champagne when it’s raised out of a well.