The MOLA AUV—multimodality, observing, low-cost, agile autonomous underwater vehicle—is a portable, but powerful, autonomous robot for ocean exploration. Equipped with sensors and algorithms for high-resolution navigation, imaging, and mapping, the MOLA AUV is ideal for operating in shallow coastal waters around Paleochori Bay and Spathi Bay, where access is limited to small boats or shore deployment. The vehicle’s compact size and vectorized thrusters configuration enable precise control over all six degrees of freedom—forward, lateral, heave, roll, pitch, and yaw—allowing it to navigate rugged underwater terrain with ease.

Using data collected from the vehicle’s forward-looking sonar, stereo cameras, and laser scanner, the CoMPAS Lab will generate detailed maps and 3D photogrammetry reconstructions that geologists can use to characterize vent features, especially bacterial mats and mineral precipitates that are key indicators of hydrothermal outflows. 

The team will first create accurate maps of areas of interest based on NKUA collaborator Paraskevi Nomikou’s earlier work on the shallow-marine hydrothermal fields of Paleochori Bay. Then, conditions permitting, they plan to extend mapping efforts to deeper hydrothermal vents in Spathi Bay, which have not previously been surveyed or studied in detail due to their depth.

The fieldwork in Milos is an important opportunity to validate recent advances in autonomous navigation, control, perception, and mapping in real-world environments, while collecting new field data for continued algorithm and system development. Together, these deployments underscore the CoMPAS Lab’s strategy of rapidly moving technologies from development to field validation and applying scalable marine robotics to challenging scientific problems.

Distributed acoustic sensing (DAS) uses fiber-optic cables as dense sensor arrays. By measuring the phase changes in laser light along the cable, scientists can detect disturbances on the seafloor, including earthquakes, underwater landslides, and fluid seepage. These processes can be relatively small-scale, yet they play a major role in shaping the seafloor.

MBARI’s Seafloor Processes Team has developed Geo-Sense, a portable DAS system that can be deployed wherever there is a seafloor process of interest. The team has adapted Geo-Sense components into a portable travel case to test the effectiveness of DAS technology for detecting and quantifying hydrothermal venting.

The DAS system will be installed onshore in Paleochori Bay, monitoring backscatter along a cable running 700 meters (approximately 2,300 feet) offshore to a depth of 15 meters (49 feet). The team will work with local divers to strategically place the cable near active vents to detect acoustic signals associated with bubble emissions from hydrothermal vents and estimate their seepage rates. These signals are expected to vary across different areas of the bay, potentially reflecting differences in bubble size and nucleation processes. The temporal distribution of these acoustic events will offer insight into evolving gas seepage patterns and may reveal correlations with environmental or volcanic activity. 

The team will deploy hydrophones and cameras near the cable to collect complementary data about the release of gases from the seafloor. The hydrophones are underwater microphones that record the high-frequency sound of gas bubbles percolating from the seafloor, while the Bubble Cam is a new stereo-imaging system developed by MBARI engineers to quantify gas seepage. Data from both instruments will provide context for reviewing acoustic signals recorded by the DAS system.