Ocean exploration, like space exploration, requires a variety of toolsincluding multimillion-dollar research vessels, submersibles and various underwater helpers. Many people know about manned submersibles such as Alvin, which bring scientists to the ocean depths. Unmanned vehicles bring the secrets of the deep to the scientists, and are nearly as valuable to undersea exploration. AUVs (Autonomous Underwater Vehicles) such as ABE are untethered and programmed to work on their own. ROVs (Remotely Operated Vehicles) such as Jason II are tethered to a research vessel and controlled by a pilot. In addition to vehicles, scientists use other complex tools to explore the seafloor, such as samplers to grab and sensors to measure and analyze both fluids and gases.