Probing, Prying, Spying

Scientists test the water

Relatively little is known about oceans because they're so vast and deep. In many ways, studying the oceans is much like studying other planets. Scientists have had to devise ingenious techniques to gather data over immense areas and to penetrate the depths.

Although oceanographers will always need to go to sea in ships to collect samples and make precise measurements, the only way to survey large areas simultaneously is to take the long view --from satellites in space.


Moorings "mind the lab" for long, uninterrupted periods, because ships can't stay out of port indefinitely. These vertically anchored cables suspend equipment in the water or place other devices on the sea floor to record data on currents, water temperature, or chemistry. Later, the ship returns, acoustically signals the anchor to release, and retrieves the mooring and equipment §.

Submersibles Submersibles take scientists in for close-ups. Once, scientists could only drag nets through the water or over the ocean floor--a process that mainly captured slow-movers and often damaged the animals collected. Now, advanced diving vessels and robotic submersibles armed with special collecting devices and video cameras catch deep-sea organisms in the act and leave them intact.

Reversing Nansen bottles sample at specified depths. Bottles (named after the Norwegian oceanographer who invented them) are attached to a wire at measured points and lowered into the water. A cylindrical "messenger" sent down the wire triggers the bottle to reverse, break off a thermometer inside (to record temperature at that point), take a sample, and send a messenger to the next bottle.

CTD sensors (for conductivity/ temperature/depth) give continuous on-the-spot readings. Subtle changes along the water column in temperature or salinity may be important. To locate them, scientists lower a CTD, attached to sampling bottles so that data and water are collected at various depths §.

Standard sea water sets the standard for water sampling. Oceanographic institutes need a way to standardize their salinometers (to measure salt levels). To create a common standard so that data can be compared around the world, researchers use sea water prepared to an accurately known level of conductivity and a salinity of 35 parts per thousand §.

Core drilling hits pay dirt on the ocean floor. Sediments have accumulated undisturbed on the deep ocean floor, providing the most complete geologic record of the past 200 million years. Studying sediments reveals biological, physical, and chemical information about the oceans and the ocean floor and continents, as well as details of the earth's past climate §. Cores have provided evidence of changes in sea level due to ice ages, as well as major geologic events such as the asteroid strike that may have caused the extinction of dinosaurs §.

More Information

Ocean Planet Exhibition Floorplan

gene carl feldman ( &
Judith Gradwohl, Smithsonian Institution (Curator/Ocean Planet)