MOLA off-bottom…100 meters…50 meters…20 meters…at surface…Vehicle on deck!

And just like that, our 10 days in Milos come to an end. After 16 dives with a maximum depth of 101 meters (332 feet), and nearly 18,760 meters (61,549 feet, roughly 11.6 miles) navigated, MOLA is back on deck, and the DAS cable has been recovered.

When we arrived, the seafloor of Paleochori Bay between 30 and 80 meters (100 to 260 feet) was shrouded in mystery. Too deep for divers and too shallow for large research vessels, our collaborators at the National and Kapodistrian University of Athens (NKUA) only had low-resolution maps of these waters. Today, we have a much clearer picture of this environment. 

Using the CoMPAS Lab’s own precise navigation and control methods, MOLA collected more than 30 hours of mapping data, including high-resolution 3D imagery for photogrammetry, imaging sonar data for mosaics and computer reconstructions, and 4K video of the vents themselves. And what an active seafloor we found! Vent after vent of rising bubbles, bacterial mats, and other geological features across Paleochori and Spathi Bays. 

MBARI engineers will now process this data and share it with our collaborators at NKUA for a thorough study, bringing us one step closer to understanding the processes that shape this island. 

There were also some personal bests along the way. Milos gave MOLA its deepest 3D mapping dive yet, a milestone that makes the CoMPAS Lab proud and fuels our motivation to keep pushing the limits of what scalable robots can do for ocean exploration. MOLA proved it can be both portable and agile: small enough to launch from a small boat, yet capable enough to navigate complex terrain. Meanwhile, our colleagues from MBARI’s Seafloor Processes Team were testing new technology for monitoring gas seeps. 

Distributed acoustic sensing (DAS) transforms a fiber-optic cable into hundreds of closely spaced sensors capable of detecting tiny vibrations. Senior Scientist Aaron Micallef and team were investigating whether this technology can detect and quantify gas emissions from the seafloor. Working with local divers, they placed a cable along the shallow sandy seafloor of Paleochori Bay, alongside a camera and hydrophones. They will now analyze data from the cable alongside information logged by a stereo camera system and hydrophone installed near the cable to determine whether DAS detected the vibrations associated with escaping gas bubbles. 

On one of its dives, MOLA mapped a large portion of the DAS cable, giving Aaron and his NKUA collaborators visual context to complement the data their cable collected, a great example of the collaborative spirit of MBARI.

So what’s next? The adventure to study hydrothermal vents doesn’t stop here. The CoMPAS Lab and Seafloor Processes Team are continuing our Greek adventure, this time heading to Catania, where MBARI’s MiniROV is already waiting for us in port to explore deeper hydrothermal vents and chimneys near Kolumbo. And MOLA? Our dear AUV is packing its bags for a long journey to Chile, where it will meet the CoMPAS Lab team in January for its next expedition.

Thank you, Milos, and thank you to everyone who followed along! Until the next dive!