Chris German, Chief Scientist for Deep Submergence at the Woods Hole Oceanographic Institution here in Massachusetts, has been busy finding undersea volcanoes with the help of autonomous underwater vehicles (AUVs) and remotely operated vehicles (ROVs).
With more than half the planet’s water exceeding depths of two miles, mapping the sea floor is no easy task. What’s more, technology being developed and used at Woods Hole may eventually make its way to one of Jupiter’s moons, Europa, in order to collect data from the ocean that’s thought to be buried beneath two kilometers of ice.
Up until about 15 years ago, human occupied vehicles were used for deep sea exploration. Despite the inherent limitations of cramming one or two people into a tiny submarine like the one pictured above, it remains true that humans are still far better than robots at things like decision-making and situational awareness.
While the recent trend in undersea exploration has been a shift to ROVs, a new class of autonomous underwater vehicles, or AUVs, has begun to emerge and aims to bridge the gap between all-human and all-robotic exploration.
In order to map an area of the sea floor, scientists previously had to deploy an ROV attached to a long length of cable and drag it back and forth over a target zone at a rate of 1.5 miles an hour – roughly half the speed of walking. Needless to say, mapping a large area took a long, long time. Newly-developed AUV’s, though, are able to greatly expedite the process.
Take “ABE” – the Autonomous Benthic Explorer (photo, left) — an AUV that was in service at Woods Hole until last year. It was built like an underwater helicopter, with propellers in the back and on top to allow it to maneuver easily.
Much cheaper than towing an ROV manually, ABE was able dive down to five meters off the sea floor, photograph it, then work its way back and forth along a specified region from the bottom of the ocean to the surface. ABE completed 202 dives between 1995-2008.
ABE is being replaced by a robot called Sentry, which will enter service this year. Compared to ABE, Sentry has a longer working range and can travel faster. It also has angled thrusters, allowing it to move up and down and side to side like ABE, but also at various angles too.
Along with Sentry, Woods Hole is developing a vehicle called “Nereus” – a hybrid ROV/AUV named after the Greek God of shape-shifting. Nereus will be able to autonomously dive to depths of up to 11,000 meters and can also be remotely controlled via a single fiber-optic wire while powered by an eight-hour battery. Nereus will complete its first mission in June and will be featured on the Discovery Channel.
NASA’s Galileo Project aims to explore two of the four main moons of Jupiter in the next 20 years. Io is the most volcanically active moon in our solar system with eruptions reaching above two kilometers from the surface, and Europa is thought to contain a vast ocean underneath a two-kilometer-thick layer of ice.
NASA plans to build a vehicle to explore Europa’s ocean and has contacted Woods Hole in the hopes of basing the design off of Nereus. As mentioned, Nereus will complete its first mission in June, followed by a mission in the fall to Cayman Trough, the world’s deepest ocean trench (just south of Cuba), and then eventually to arctic regions in order to simulate conditions on Europa — like how to drill through two kilometers of ice.
Woods Hole Oceanographic Institution [whoi.edu]