exist. Over the past few decades, however, a series of spectacular space missions and remarkable discoveries at home have suggested to many scientists that Earth may not be the only place in our solar system to harbour life. ch Deep in the Mexican jungle there is a cave called the Cueva de Villa Luz. It is full of hydrogen sulphide, a gas that smells like rotten eggs and, in high concentrations, is lethal to humans. Inside the cave strange life-forms have been discovered called Snotties -- so named because they resemble drops from a cold nose! They do not need sunlight to survive. Instead they eat the sulphur and warm, volcanically heated water and produce battery acid as a waste product. They are members of a class of life-forms called extremophiles, colonies of microbes that live in the most hostile conditions imaginable. Similar organisms have been found around volcanic vents in the deepest and darkest depths of the oceans, thousands of metres below the surface, and living in the intensely hot pools of water around geysers. These discoveries have led many biologists to conclude that life may exist anywhere that liquid water can be found. Sunlight, oxygen, carbon dioxide or any of the other things we usually associate with life, at least on planet Earth, are not necessary. Prof Brian Cox ... thinks it's possible aliens exist This is a fascinating discovery because as we explore the solar system we are finding strong evidence that more and more worlds have