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Deep under the ocean's surface lies a treasure trove of new life forms, fuel sources and knowledge. But, given the darkness, freezing temperatures and crushing pressure, it's not easy to get there. Indeed 95 percent of the ocean remains unexplored; we know more about the surface of Mars than we do about the seafloor. "More than half of the planet is covered by water more than 3,000 meters [two miles] deep," says Chris German, chief scientist for the deep submergence group at the Woods Hole Oceanographic Institution in Cape Cod, Mass. "Most of the life that exists on the planet exists in the oceans. But we know so little about it."
Slide Show: Manned and Unmanned Submersibles
That is beginning to change, as engineers and scientists create new submersible vehicles and probes capable of making the deep blue yonder more accessible than ever. By the 1970s, there were several small submersibles capable of taking people into the deep ocean (generally considered to be water deeper than two miles). Today, several nations—including the U.S., Russia, Japan and France—have built their own human-occupied vehicles (HOVs) and use them for scientific research.
"Humans are by most measures kind of the best in situ sensor you can get," says Andy Bowen, the lead engineer for several Woods Hole deep ocean vehicles. "The human eye and the other senses can learn things about the environment more quickly than almost any other technology." Because they have human operators on board, the systems are also easily maneuverable and can range freely, without having to stay alongside a vessel at the surface. But manned vehicles have some definite drawbacks. They're big, heavy and expensive—the newest human occupied vehicle, currently being designed for Woods Hole, has been forecast to cost $50 million—so only a handful of them have been built. There aren't nearly enough of them to carry out all the studies that scientists are interested in conducting in the deep sea.
Robotic submersibles—or ROVs, for remotely operated vehicles—are typically tethered to a ship on the surface of the water, where human operators control their movements. The machines also often carry a variety of sensors and cameras, transmitting data and images back to the surface vessel. ROVs can spend weeks, or even months, at a time underwater. (HOVs, on the other hand, can only support human life for a few days on the seafloor before having to resurface.)
HOVs and ROVs will continue to see incremental improvements, but the real advances will come in engineering so-called autonomous underwater vehicles (or AUVs), which combine the best of both worlds, Bowen says. AUVs are robotic vehicles that need no human intervention—they not only swim untethered, independent of a ship, but also are self-piloting, thanks to onboard software and sensors. "As our abilities to control or promote autonomy improve, and the behaviors that these robots have continue to become more complex," Bowen says, "it's quite possible that most of the exploration of the ocean will be done by autonomous vehicles."
The work scientists hope to undertake in coming years could lead to powerful new medicines (courtesy of some of the strange, undiscovered creatures of the deep), provide important information about climate change, and yield clues to natural disasters like tsunamis and earthquakes. German says, "It's not safe to ignore the ocean if you want to understand the planet."