Sometimes in science, you just have to be there.

		Graphic: Tethered Yearlong Spectrometer

In October 1993, for instance, oceanographer John Delaney just had to see what happened on the ocean floor following an earthquake.

When he and his University of Washington colleagues reached the Juan de Fuca Ridge off the Pacific Northwest coast in the deep-sea submersible Alvin, they found the water filled with "marine snow," vast amounts of microbial material billowing up from beneath the seafloor.

These microbes would come to be known as Archaea, a fundamentally different form of life that thrived in temperatures near boiling. And scientists now knew that life didn't just exist in the upper layers of sediments, but could be found deep within Earth's crust.

It's an observation that couldn't have been made if scientists hadn't been at the right place at the right time, said Richard Camilli of the Woods Hole Oceanographic Institute in Massachusetts.

Unfortunately, when it comes to studying the ocean depths, humans just can't be there for long.

"We don't really know all that's going on down there," he said.

That's why Camilli, an environmental engineer, envisions a day when tethered instruments and robotic subs would take the place of humans, tirelessly gathering information for months or years after their human counterparts have headed back to shore

Camilli is developing chemical sensors that might be part of such an instrument array. In particular, he is working with a Cheswick firm, Monitor Instruments Co., to build a submersible version of a mass spectrometer, a widely used and powerful tool for identifying chemicals.

Called the Tethered Yearlong Spectrometer, or TETHYS, it could operate for months on its own, checking for dissolved chemicals released from the seafloor, for biological chemicals that might reflect the health of deep sea life and for environmental pollutants.

Long-term monitoring with "mass spec" might help resolve the fate of methane released from methane hydrates, ice-like deposits in the seafloor. No one knows if this methane dissolves or ultimately reaches the surface, where it can join other greenhouse gases in the atmosphere.

"The nice thing about a mass spectrometer is that, rather than measuring only one parameter, it can measure a bunch of chemicals simultaneously," said Camilli, who designed a mass spectrometer for a robotic submarine as his doctoral project at the Massachusetts Institute of Technology.

The vision of an array of seafloor instruments continuously monitoring the environment without a human presence already is being pursued by oceanographers, with Woods Hole and the University of Hawaii establishing a pioneering seafloor observatory called the Hawaii-2 Observatory midway between Hawaii and California in 1998.

Large underwater observatories, cabled to allow real-time monitoring by scientists, also are being developed off the coasts of California and British Columbia.

A version of TETHYS should be ready within a year and will get an early tryout at the Martha's Vineyard Coastal Observatory, Camilli said. It also could be incorporated into the Pacific seafloor observatories and might see use in a 2007 Woods Hole expedition to study the volcanic underwater mountain range in the Arctic called the Gakkel Ridge.

Mass spectrometry has been in use in various forms for decades. The technology varies but, in its simplest form, mass spec involves taking atoms or molecules from a sample, electrically charging them and then using electrical fields to accelerate them to a uniform velocity. These particles then pass through a magnetic field, which deflects them. By measuring the degree to which the particles are deflected, the mass spec can calculate the particles' mass, which in turn identifies what type of element or molecule it is.

Mass specs can be room-sized instruments, but even small ones can fill a tabletop; they all generally require lots of power and regular calibration by highly trained engineers. Prices can range from hundreds of thousands of dollars to millions.

"Monitor's goal is to make mass spec a tool for the common man," said Anthony Duryea, president of the Cheswick company. "We set out to miniaturize and simplify the use of mass spectrometry and also make it portable. It's taken us 10 years to do this."

What they developed is a very compact device called a cycloidal mass spectrometer. Rather than electromagnets, it uses permanent, powerful rare earth magnets to deflect particles.

A version Monitor has developed for NASA, which plans to use the devices to sniff for rocket fuel leaks aboard the space shuttle, is just 2 inches in diameter and a half inch thick, Duryea said. The company also is developing a medical version, which can analyze a person's breath to determine if his stomach harbors H. pylori, the bacteria that can cause ulcers.

It's an elegant design, Camilli said, which can operate at much lower power than the typical electromagnetic device. That is a big advantage for autonomous devices such as TETHYS that must operate using batteries for extended periods.

A major obstacle to underwater mass spec is that fact that mass spectrometers must maintain a near-perfect vacuum. That hasn't been a problem for NASA planetary and space probes, such as Viking and Galileo, that carried mass spec instruments; outer space is a near-perfect vacuum to begin with. But the deeper underwater you go, the harder it is to maintain a vacuum.

"Every 10 meters you do down in the water column, you increase the ambient pressure by one atmosphere," Camilli explained. "At 6,000 meters, you're at 600 atmospheres of pressure."

That's where another Monitor innovation comes into play. Rather than maintain a vacuum using a mechanical pump, which would have to pump its exhaust out against the high ambient pressures of the deep sea, Monitor has developed a pump without exhaust and without moving parts.

Called a NEG-ion pump, it relies in part on a "non-evaporable getter," or NEG, a material that traps gases. And those particles that the getter doesn't get are handled by the ion pump, which uses electrical fields to embed the particles into a layer of titanium, said Mark Wilson, Monitor's marketing director.

Camilli hopes TETHYS can be built for a fraction of the cost of a conventional mass spec. The project is sponsored by National Science Foundation, the Office of Naval Research and the National Oceanic and Atmospheric Administration.

Being able to analyze chemicals in sea water at depth promises to be an important tool, Camilli said, because removing water samples from the deep sea can change the samples' physical properties. Water at high pressure, for instance, contains a greater fraction of dissolved gas; that's why deep-sea divers can suffer the bends if they surface too quickly.

"It's kind of an exciting time in oceanography," Camilli said. "We're finally getting the tools, the technology, that allows us to see in places that we've never seen before."