Methane hydrate eruption accident aboard the Sonne

The methane hydrate eruption aboard the RV Sonne turns a seabed sample into an uncontrolled breach. As a video grab cuts into hydrate crowded with worms, the deposit gives way and gas surges upward, striking the vessel’s stern and sweeping across the deck. A Statoil technician is killed, the planned rendezvous is cancelled, and the scientists must confront the possibility that the worms are changing the very seabed they came to study.

Sampling the worm-covered hydrate

The operation begins with the video grab descending through plankton toward a seabed that appears briefly on the monitors as a barren, lunar landscape. At a depth of 714 metres, the view changes: mussels, normally colonizers of hydrate, are obscured by writhing worms. Sigur Johanson sees jaws extend from their tube-like bodies and tear at the mussels. Bubbles rise from the seabed with tiny, shimmering fragments of hydrate. This is not simply a sample site populated by an unfamiliar animal; the worms appear to be feeding amid a layer of methane ice.

At Gerhard Bohrmann’s signal, the grab descends again. Its iron jaws disappear into the deposit and clamp shut. The depth readings change rapidly, pause, then accelerate. The grab has broken through and is sinking, meeting no resistance. Bohrmann orders it pulled up. As it rises, its cameras reveal a vast hole and swollen bubbles surging from within. A stream of gas engulfs the grab, and the monitor image vanishes in a whirlpool.

The blowout reaches the deck

The danger becomes physical as the RV Sonne accelerates away from the site. The sea begins bubbling violently and white lumps shoot to the surface; the grab’s cable tightens against the vessel’s stern. The first officer warns two Statoil technicians standing beneath the A-frame to move away. A geyser engulfs the stern area, and the grab rises through the surface. Its jaws swing sideways across the deck. One technician ducks; the other hesitates and stumbles. The first officer tries to pull him down, but the swinging equipment strikes him. He is killed on impact.

Tina Lund and Johanson run toward the motionless technician, but the first officer tells them not to touch him. Lund then turns to the equipment and calls for the grab to be opened so whatever remains can be put into tanks. The gas bubbles gradually subside as the vessel moves away, and the final pieces of methane ice rise and disintegrate at the surface. The accident has transformed a sampling operation into an emergency involving both a fatality and the loss of control over the hydrate release.

What the sample reveals

The grab releases hundreds of kilos of ice and sediment onto the deck. Sailors and scientists try to preserve the hydrate in liquid-nitrogen tanks, while the worms brought up from the seabed lie among the material. Most have not survived the rapid change in temperature and pressure. Johanson examines a clump of ice crossed by dark channels and scattered with worm remains. Other pieces are riddled with holes; crater-like breaches and slimy trails mark the deposit. The damage suggests that much of the destruction took place beneath the surface, along the routes the worms had tunnelled.

Johanson also notices slime that looks like the remains of bacterial colonies. Bacterial mats occur on hydrate surfaces, but their presence within the ice raises a further question about the worms’ relationship to their environment. Bohrmann describes the incident as a blowout: the grab penetrated more than twenty metres into the hydrate, releasing gas. The deposit is at least seventy to eighty metres thick, or had been before the breach. The sampling accident therefore supplies evidence of a deposit with substantial depth and of worm activity penetrating far below its visible surface.

Changed methods and interrupted research

Bohrmann says the next sample will be taken with an autoclave corer rather than another grab. The five-metre tube is designed to preserve seabed conditions: valves seal the sample before retrieval, while temperature and pressure remain controlled. In this way, sediment, ice, mud, pore-water, and local organisms can be brought up with their layers intact and without the abrupt environmental change that killed most of the worms from the grab. The sealed cores are stored upright in a walk-in freezer. They cannot be analysed aboard the RV Sonne; the researchers will need the GEOMAR deep-sea simulation chamber to recreate suitable conditions.

The blowout also changes the expedition’s immediate course. A planned rendezvous with the Thorvaldson research vessel at the site of a proposed subsea unit is cancelled. The RV Sonne heads for Kristiansund to hand over the dead technician and transport the samples to a nearby airport. The researchers have collected evidence, but their work is interrupted by the cost of obtaining it.

Significance of the accident

The incident binds together the expedition’s scientific question and its practical danger. The worms are not merely an unknown species to be classified: their tunnels and feeding activity are associated with extensive damage within methane hydrate, and the grab’s penetration turns that altered deposit into a sudden gas release. At the same time, the accident demonstrates that the instrument used to investigate the seabed can become part of the hazard when it breaks through the deposit.

The change to sealed coring reflects a shift from forceful extraction toward preserving the conditions of the deep-sea environment. The researchers still need to understand the worms, but the accident makes the method of inquiry consequential: what is disturbed, how it is brought to the surface, and what evidence survives the journey all shape what can be known. The fatality and cancelled survey leave the investigation unresolved, while the preserved cores offer a safer route to examining the hydrate and the organisms within it.