A new type of underwater robot has completed sea trials in Monterey Bay, California. Developed by the Monterey Bay Aquarium Research Institute (MBARI), the Woods Hole Oceanographic Institution (WHOI), and partners, the Mesobot is a semi-autonomous robotic submersible designed to study the marine twilight zone of the mesopelagic region.

The mesopelagic zone is sort of the middle ground of the ocean. Located between 200 and 1,000 m (660 to 3,300 ft) in depth, it's a region where only one percent of the ambient light reaches down. There isn't enough light to support photosynthesis, but it's still home to a surprising variety of life, including bristlemouths, blobfish, bioluminescent jellyfish, and giant squid.

It's also an area of great scientific, commercial, environmental, and military interest because it's through here that the "diurnal vertical migration" takes place. Called the greatest migration on Earth, it occurs twice a day as planktonic animals ascend into what little daylight there is, and then descend again in the evening.

This affects everything from feeding patterns of swordfish, tuna and other large animals, to carbon capture and anti-submarine warfare, but very little is known first-hand about what happens in the mesopelagic, so Mesobot has been under development since 2017 with the help of Stanford University, and the University of Texas Rio Grande Valley.

Looking rather like a large cooler, Mesobot is designed to operate autonomously for up to 24 hours as it tracks and studies swimming and drifting animals in the twilight zone. It's based on previous Remote Operated Vehicles (ROVs) that have been produced at MBARI by Bruce Robison, Steve Haddock and others

It's designed to study marine life with as little disruption as possible through the use of low-light 4K cameras, lamps that produce red lights that are harder for animals to see at such a depth, and large, slow-turning propellers that create very little turbulence and noise.

According to MBARI, Mesobot is a tethered robot that is controlled and powered from the surface using a fiber-optic cable until it reaches its operating depth, then it's released and control is switched to the onboard computer. To help tack Mesobot, the tether was equipped with MBARI's "SmartClump," which is a bundle of sensors and cameras.

The recent test program included putting Mesobot through its initial paces in MBARI's indoor saltwater test tank, then taking it out into Monterey Bay aboard the research ship Rachel Carson for three days of sea trials. These consisted of five dives to a depth of several hundred meters and not only helped to test the robot, but also procedures for launch and recovery.

Source: MBARI

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