An unmanned, deep-sea research sub dubbed Nereus was lost while diving 6.2 miles (10 km) beneath the surface, and likely imploded during its mission, reports indicate.
The hybrid remotely operated vehicle (ROV) was exploring the Kermadec Trench - one of the ocean's deepest spots - northeast of New Zealand on Saturday, representatives for the Woods Hole Oceanographic Institution (WHOI) have confirmed.
According to Live Science, surface debris suggests that Nereus imploded due to intense pressures. The deep trench has pressures of about 16,000 pounds per square inch (psi) - comparatively, humans experience 15 psi at sea level.
The $8 million robot, primarily funded by the National Science Foundation, was working as part of a mission to explore the ocean's hadal region from 6,000 to nearly 11,000 meters deep.
"Nereus helped us explore places we've never seen before and ask questions we never thought to ask," WHOI biologist Timothy Shank, who managed the sub, said in a news release.
"It was a one-of-a-kind vehicle that even during its brief life brought us amazing insights into the unexplored deep ocean, addressing some of the most fundamental scientific problems of our time about life on Earth."
Nereus operates remotely via an optical fiber tether and also as a free-swimming autonomous vehicle, and was 30 days into a 40-day expedition to explore the deep-ocean trench aboard the research vessel Thomas G. Thompson.
Researchers lost contact with the ROV while it was collecting images and samples of unusual sea life that can survive in the deep-sea trench, Live Science reported. The team is now collecting surface debris in hopes of revealing more about the nature of the failure.
"Extreme exploration of this kind is never without risk, and the unfortunate loss of Nereus only underscores the difficulty of working at such immense depths and pressures," WHOI Director of Research Larry Madin noted in the release.
In addition to the Kermadec Trench, Nereus was one of only four subs to successfully reach Challenger Deep in the Mariana Trench - the deepest point in the ocean.