The recovery ship Horizon Arctic has now delivered all the debris it was able to collect from the shattered remains of the Titan submersible on the Atlantic seafloor.
As shown by the amount of material that came ashore, the ship's deep-sea robot managed to bring up significant components. These may yet help investigators get to the root cause of the Titan's catastrophic implosion 11 days ago that killed five people. Weld Neck Flanges
Quayside workers in St John's in Newfoundland attempted to cover the fragments with sheeting, but some pieces were still clearly identifiable.
One of the most obvious was the front titanium end cap from the cylinder-shaped, carbon-fibre sub.
Looking rather like a metal doughnut, the hole in its middle is where the viewport window would have been.
The crane's lifting sling went right through the hole. We don't know where the acrylic window is now. Concerns had been raised about its strength, about whether it could cope with the pressure at 4km depth. But nothing can yet be read into its absence in the pictures recorded in St John's.
Also brought ashore were what appeared to be the titanium flanges. These are the metal rings glued to either end of the Titan's carbon fibre cylindrical hull. The flanges would then have made contact with the end caps.
The flanges and their join to the carbon fibre will be central to the investigation now under way with US and Canadian authorities.
"I think the key parts to look at are the interface between the acrylic window and the titanium, hemispherical domes, or end caps; and also the area where the carbon fibre would have been bonded to the titanium flanges," said Blair Thornton, professor of marine autonomy at the UK's Southampton University.
"You can see... that both of those components were recovered which is as much as we can hope for in order to further the investigations," he told BBC News.
Several bags of debris were lifted on to waiting trucks. We have no idea what was in them. Could there have been pieces of the carbon fibre hull itself?
If there are, investigators will want to examine them for any evidence of the carbon layers beginning to separate - a process known as delamination - especially at the point where they joined the flanges. Carbon fibre layers can start to separate in extreme settings.
One of the larger items to come ashore was the rear equipment bay. Although covered by a pointed tail cone when diving, it was an open cage. It's obvious from the pictures that it suffered extensive damage as it was ripped away from the sub.
Notice the long protruding rod. This is an antenna that would ordinarily connect with the Iridium satellite phone network when the sub was at the sea surface.
The antenna would have been independently powered and the fact that no message was received over this system after the Titan began its dive was a strong indication during the search phase that the vehicle had never come back up.
The long metal struts lowered on to the waiting trucks are what's left of the landing frame, which the Titan used to sit on a flat surface, such as in the workshop or on its launch barge. The recovered sections would have been attached to the titanium end rings.
The large, white-coloured panels seen at quayside were part of the exterior cladding or fairing from the sub. They were used to cover wires and tubes that ran along the outside of the carbon fibre hull.
Some have described these panels as the hull fragments themselves, but pieces of the carbon fibre pressure vessel would be black, thick and rigid. These white panels in contrast bent as they were lowered on to the truck.
What we didn't see being taken off the ship were any containers that might have been used to move humans remains. The US Coast Guard says potentially it now has such material.
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