If you thought acid-dripping aliens were the stuff of science fiction, think again. Beneath the Guadalupe Mountains of New Mexico, weird life forms are eating our planet!

In a mineral-clad cave network the height of a 30-story building and the size of six football fields, a geological puzzle led to the discovery of some of the strangest creatures on Earth, which could point to life on other planets. 

Most limestone caves are formed by water percolating through rock. Through erosion and mild acidic attrition this slowly wears away limestone to form underground hollows. The Carlsbad Caverns of New Mexico, however, are coated in gleaming white gypsum, creating wonderful crystal chandelier-like structures. But gypsum is soluble in water, so how can it remain here? 

The search for an answer took scientists to other caves, further south in Mexico, filled with noxious hydrogen sulphide gas and sulphuric acid. There they discovered microbes, insects, spiders, crabs and fish all flourishing in the dark and caustic atmosphere, along with “snottites” – stalactites of sulphur-eating mucous-like bacteria that drip sulphuric acid onto the surrounding limestone. 

The question is, if these creatures can exist in such extreme conditions here on Earth, is it possible there could be similar life in the poisonous atmosphere of other worlds?

NOVA: Mysterious Life of Caves - Thursday 7 June at7.50pm