The full-ocean depth hydrophone (top left) attached to the CLOSP lander along with a conductivity, temperature and depth sensor (CTD). The lander also stores geological and biological samples collected by the submersible. Photo Credit: Kathy Sullivan/Caladan Oceanic
PMEL Acoustics Program and Engineering Development Division participated as part of a memorandum of understanding between NOAA and Caladan providing subject matter expertise on pressure sensors and acoustics during the June mission in the Mariana Trench to map the Challenger Deep with pressure sensors and collect oceanographic data. A full-ocean depth hydrophone was deployed during the Ring of Fire Expedition at Challenger Deep. The hydrophone was deployed on a lander with several deep-ocean pressure sensors over two cruises in the Challenger Deep basin. In addition, water samples for environmental DNA analysis have also been collected.
The first dive was completed on June 8 by Kathy Sullivan and Victor Vescovo aboard the Limiting Factor, a two-person submersible built by Triton Submarines and Caladan Oceanic. The recordings from the hydrophone are also part of acoustics research conducted by Woods Hole Oceanographic Institution to determine how sound waves propagate in the deepest parts of the ocean.
PMEL successfully first deployed the hydrophone in 2015 to establish a baseline for noise in the ocean’s deepest location. The recordings captured a baleen whale’s call, a magnitude 5.0 earthquake, an overhead typhoon and ship traffic noise.