The crystal fuel

Natural History, May, 1997 by Kevin Krajick

The U.S. Navy also has shown interest. Hydrates change the acoustics of ocean bottoms in ways that can distort sonar signals used to track submarines. According to unclassified documents, researchers from the Naval Research Laboratory have been towing a new, 2,000-foot-long, deep-sea seismic apparatus over suspected hydrate sites to make better maps of them.

Scientists are even looking to other planets. Based on pressure-temperature calculations, among other evidence, hydrates of carbon dioxide, methane, nitrogen, and ammonia are thought to make up some of the geology of icy moons orbiting Saturn, Uranus, and Neptune. They may exist on Mars. The earthly relevance: Our planet may have started out as a barren core of iron and silicate with no atmosphere, like a house without furniture. That's where the hydrates come in. They are good at trapping all kinds of molecules. Some scientists believe they are what comets are made of. Earth may have gotten some of its water, carbon compounds, and nitrogen--building blocks of life--when comets rained them down in hydrates, which then broke up into gases and water. The hydrates under the earth today are likely to remain as mysterious as these possible ancient ones. For now, we can only capture them briefly before they fizzle and disappear.