Although the Benthic Rover II is a small car, it has fat tires that make it feel more like a tank. This, together with two flotation devices that look like googly eyes, gives the Benthic Rover II a WALL-E-like vibe. BR-II, however, does not explore a trash-strewn area. Instead, it roams the 13,000 foot deep Pacific seafloor. The robot's mission is to explore the squishy terrain looking for clues as to how carbon is processed in the deep ocean.
The mission starts with a wild ride around the coast of Southern California, approximately 180 miles. The scientists at Monterey Bay Aquarium Research Institute lower BR-II in the water, and then... drop the robot. The robot falls completely free of any ties and remains there for 2 1/2 hours. It lands on vast plains, which are great stretches of what might be called muck. MBARI's electrical engineer Alana Sherman is coauthor of a Science Robotics paper that describes the robot's adventures. "This is why it's a tracked vehicle and it has these really large treads." This extra area distributes the robot’s weight so that it doesn't sink in the sand.
The deep sea is the ideal place to find the best way to torture a robotic being. The water at these depths is extremely cold, salty (and thus corrosive), as well as highly pressurized. There's a lot of liquid pushing down upon the robot.
This robot, like the Mars rovers must be autonomous. It's actually more difficult to monitor a robot that is 13,000 feet deep than a rover on another world. Radio waves travel well through space. It's just that it takes them up to 20 minutes to travel between Earth and Mars. Good luck remote piloting a rover with this kind of delay. Radio waves don't like water. Instead, BR-II uses acoustic waves to communicate with another robot. MBARI scientists release a floating glider from the shore four times a calendar year. It is essentially a surfboard that costs a lot. The glider travels to the exact location of the rover, pings it and collects status updates.
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MBARI scientists cannot just sit in their labs and control the rover. It must be controlled by itself. Its instructions are easy. It is parked on the seafloor and lowers two oxygen sensors to the muck. The robot can measure the biological activity of sediment by placing two oxygen sensors on the seafloor. Microbes consume oxygen and expel carbon dioxide. Fluorescence cameras are also installed on the rover. These emit a blue light that makes organic matter's chlorophyll glow. This allows the robot to see how much debris from the surface waters is making its way to the seafloor, also known as "marine snow".
After sitting in this position for 48 hours, the rover moves forward 33 feet. That's all. Sherman says that Sherman doesn't know whether it drove off a rock or not. All it knows is that I have to go forward 10 metres. "Fortunately, there aren't any cliffs nearby, so we use the simplicity of our environment to keep it more simple."
The problem is that the large treads can make a mess on the seafloor. Sherman says that even though the current is very slow, it doesn’t take long to create a dust storm. Sherman says, "We always want it to be driving into current so it can push sediment that has been disturbed behind us." The rover uses a sensor to determine the direction of the current and then drives straight for it.
This is how the benthic robot moves for over a year unsupervised: park, take measurements and move 33 feet. Repeat. The scientists then take the boat out to recharge it.
