Monday, November 23, 2015

Wrecks: The Antikythera

Jo Best has an article in the "TechRepublic" about the technology being used to find deep wrecks. The next three days will be drawn from her article.


The  Antikythera is best known for one of its wreck's artifacts: The Antikythera Mechanism.
Thought to have been built at the end of the second century BC, the mechanism is considered the first programmable computer, before the birth of Christ. Small and bronze, it is an intricate series of gears and dials. The mechanism could be used as a calendar, to track the phases of the moon, and to predict eclipses. It is an object out of time: no other artifact as complex was built during the thousand years after the mechanism's creation—that we know of.
The Antikythera mechanism was named after the shipwreck on which it was discovered. Having sunk to the bottom of the sea in the first century B.C. taking the mechanism with it, the shipwreck lay undisturbed until 1900, when a group of Greek sponge divers discovered it and began bringing its treasures to the surface. The ship is huge. The true size of the ship could be over 200 feet in length, putting it in the same ballpark as HMS Victory, the warship commanded by Admiral Lord Nelson during the Battle of Trafalgar. The only other known ships of the era that were larger were the pleasure barges that the Roman emperor Caligula used to cruise across Lake Nemi.
After the death of one diver and two others becoming paralyzed, operations to recover the artifacts were brought to a halt, but not before statues, ceramics, and the mechanism itself were brought up.
In 1953 and 1976, marine explorer Jacques Cousteau led the next expeditions to the wreck. Again there was difficulty in access but artifacts were retrieved.
Recently the Greek government invited a team from the Woods Hole Oceanographic Institution (WHOI), headed by Dr. Brendan Foley, to begin the first significant excavation of the wreck since the Frenchman's over 40 years ago.
The team is using an autonomous underwater vehicle equipped with stereo cameras. Using an algorithm called SLAM (simultaneous localization and mapping), the imagery from the stereo cameras can be knitted together to make an extremely precise map of the seafloor. During a few days in June, the robot created 10,500 square meters of map, with a resolution of 2mm. A separate remotely operated vehicle (ROV) carrying metal detecting equipment is also being used to spot hints of bronze or iron-carrying objects lying in the water.
Information from the ROV will be overlaid on top of the data from the 3D map generated by the autonomous underwater vehicle to build up a heat map of where the team should direct their excavation efforts when they return to the site later this summer.
"Putting humans in the water is always the option of last resort because we have to eat, we get tired and we're really not that efficient underwater. With the rebreather, we increase that efficiency, but it's still we're only want to put people down when there's no other way to do the job," Foley said.
And there is a second wreck, maybe a companion or maybe older, 400 years before Christ.

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