A cave of secrets beneath the desert

As Carlsbad Caverns' cave specialist, Rod Horrocks helps to create a living laboratory for researchers, including Nasa scientists who search for life on other planets.

A towering stone pillar emerged in my headlamp like a petrified cake dripping icing. Above it, another speleothem tapered downward, a swollen drop of water glinting at its tip.

I was 750ft beneath New Mexico's Chihuahua Desert with ranger Rod Horrocks, the cave management specialist at Carlsbad Caverns National Park.

We were exploring Left Hand Tunnel - one of the park's undeveloped caves, accessed only by scientists and permitted tours.

"Put on your gloves and follow me," Horrocks said as he disappeared into a narrow side passage.

After carefully crawling over a sturdy lattice of bone-like formations, I saw him pointing to a series of pearly, tomato-sized spheres in varying stages of inflation clinging to the wall. "These are hydromagnesite balloons," he explained.

"They're fairly rare." Concentrated magnesium left by water coats the wall, leaving a thin skin, and gases from chemical reactions trapped underneath gently inflate them.

The impossibly delicate balloons underscore that Carlsbad is a living cave system still in a state of formation after 250 million years.

Horrocks has been a cave management specialist with the US National Parks Service for the last 24 years, and traces his passion for caving back to a Missouri rock quarry he visited with his father when he was seven.

"We were looking at rocks when these two teenagers emerged from a hole and said they had been exploring a cave that goes all the way through the mountain," Horrocks said.

"I wanted to go in, but Dad wisely said no. So I went to the library and read every book I could get on caves. I was hooked."

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