Though they were originally searching for deep sea organisms in January, a group of researchers made a very different discovery. While trawling and taking pictures of the seafloor in tropical Atlantic waters about 5,000-5,500 meters (16,400-18,000 feet) below the surface, the crew discovered their gear was getting caught up on unknown objects. When the equipment returned to the surface, they were stunned to find that it was actually manganese nodules from a deposit much larger than any previously discovered in that ocean. The joint announcement comes from the University of Hamburg and GEOMAR Helmholtz Centre for Ocean Research in Kiel, Germany.
"We did not expect that at this point," lead scientist Colin Devey said in a press release.
Nodule formation is an incredibly painstaking process. Manganese hydroxide (and other metals including zinc, copper, iron, and cobalt) crystallizes around small fragments of deep-sea bone, rock, or fossils, and it can take millions of years to even add a centimeter onto the nodule’s diameter. While nodules can sometimes have a slightly irregular shape or look somewhat flattened, these particular specimens were much rounder than what is normally found.
Devey’s team suspects that some of these can be over 10 million years old, as the largest nodules discovered in the deposit were roughly the size of a bowling ball, though others were as small as a golf ball. While nodule deposits have been found in the Atlantic before, the size of this particular location is quite special.
”Manganese nodules are found in all oceans. But the largest deposits are known to occur in the Pacific. Nodules of this size and density in the Atlantic are not known," Devey explained.
Cross section of a manganese nodule is shown on the left with the exterior of the nodule shown on the right. Image credit: Thomas Walter
"This discovery shows us how little we know of the seabed of the abyssal ocean, and how many exciting discoveries are still waiting for us," added Angelika Brandt from the University of Hamburg. "At this station, very few organisms were found in the nets which captured the manganese nodules. It is quite possible that living creatures find the immediate vicinity of the nodules quite inhospitable. The second haul with the epibenthic sled at this station, which sampled over a continuous manganese crust with a thick layer of sediment on top, was quite different. Here the net collected many organisms which we were able to see with the naked eye, and we are already looking forward to the analysis of this sample.”
Because of their impressive age, the researchers will examine the nodules in hopes of finding clues about the Earth in the past, such as indications of changing ocean conditions or even clues about climate. Though the team might not have expected to produce geological specimens during their 42 days at sea, they intend to embrace the nodules, while still proceeding with their original line of research.
"We will continue our planned program. But the samples obtained here will definitely be examined in detail in our land-based laboratories. We are now excited to see what surprises the Atlantic might still hold for us," Devey concluded.
[Hat tip: LiveScience]