Scientists are at a loss to explain the strange tracks discovered after a robot was sent four kilometres below the Pacific Ocean’s surface, between Mexico and Hawaii.
The massive markings measure 2.5 metres long and 13 inches deep and and lie too deep for any known animal to have made them.
Around 3,500 individual depressions were discovered by a deep-diving drone as part of a British study from the National Oceanographic Centre (NOC) in Southampton.
Scientists have already ruled out mining and other commercial operations to be responsible, and experts also agree they are too huge to be created by known deep-sea animals.
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