2,000 year old 'computer' discovered: How tech and shipwrecks are rewriting human history

Using robots, underwater iPads, 3D printing, and other new tech, scientists are discovering shipwrecks that are rewriting our history. Read the inside story of the Antikythera and two other breakthrough explorations.

Under oceans across the world, hundreds of shipwrecks lie silent and forgotten. Having set sail to discover, trade, or wage war, the boats never reached safe harbour and exist now as time capsules beneath the waves.

When they took to the seas, some of these vessels were the state of the art, laden with some of the most advanced technology of their era. Now, thanks to the most advanced tech of our time, some long-sought wrecks are finally being found and explored for the first time.

TechRepublic talked to the teams behind some of the most high-profile shipwrecks to be discovered in recent years to find out how they've located the ships and uncovered their secrets—including a 2,000 year old device that may have been the world's first computer.

The Antikythera

If you thought the computer era started with the Colussus, or even with Babbage's designs, you'd be wrong. The advent of computing began before the birth of Jesus, with a small bronze mechanism that was lost under the sea off Crete for over a thousand years.

Thought to have been built at the end of the second century BCE, the Antikythera mechanism is considered the first programmable computer. Thanks to 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's an object out of time: no other artefact 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 BCE 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.

After the death of one diver and two others becoming paralysed, operations to recover the artefacts 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, bringing an assortment of objects, including more statues, coins, and gemstones. Due to the depth of the wreck and the diving technology of the period, divers could only spend a handful of minutes investigating the ship at a time or risk the bends that proved fatal to the first expedition.

Now, after time and technology has moved on, 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. If Cousteau and his team made sprints to the Antikythera, the WHOI exploration is set to be more of a marathon.

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Archaeologists discovered the Antikythera mechanism and dozens of other artefacts.
Image: Brett Seymour, EUA/ARGO)

"We've been taking this steady incremental approach to the shipwreck, building the foundation of knowledge about it, then posing specific research questions, trying to answer them, and seeing what the next phase brings. When we first got to Antikythera in 2012, one of the questions we had was, does the island hold a whole lot of submerged cultural resources or is this the only shipwreck out there?" Foley said.

Investigators had only scratched the surface of the Antikythera in the last nearly two thousand years. A second wreck—mentioned in passing by Cousteau's team but never really explored—had been keeping the first, better-explored ship company all these years, practically untouched.

Foley team set about circumnavigating the island of Antikythera, off whose coast the wreck lay, carrying out technical dives over a period of eight days, where they mapped everything human-made from the sea's surface down to its floor, 45 meters below.

When Cousteau's team had spotted the second wreck, they saw amphorae that looked probably Roman in origin—meaning the wreck could date from any time up to the fourth century BCE.

"We were the first archaeologists to see this [second] site and immediately we recognised that it had the exact same ceramics as the treasure wreck just up the coast" where the mechanism had been found, said Foley. The similarities between the two wrecks raised questions. Was the second wreck, dubbed Antikythera B, another ship that had sunk around the same time as the first Antikythera wreck? A second ship travelling in convoy with the Antikythera? Or something else entirely?

The debris trail stretching the 300 meters between the two ships looked to be continuous, suggesting that the two wreck sites were part of one larger ship that had split into two parts. Foley's team will be testing the hypothesis over the next few visits to the site, using technology to help them determine the true origins of the second wreck.

As it has every year since since 2012, the team returned to Antikythera this summer to probe the wreck further, examining the area between the two wrecks and using both human divers and robots.

The team is using an autonomous underwater vehicle equipped with stereo cameras. Using an algorithm called SLAM (simultaneous localisation 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.

By focusing excavation efforts on areas that show a higher density of metal, the excavations could potentially turn up more fragments of the Antikythera mechanism (only half of the system has been recovered to date). While such a discovery would generate headlines, tiny flecks of lead may have equally fascinating stories to tell.

If any lead artefacts are recovered, the team will take microscopic samples from them and send them away for spectroscopic analysis. By comparing the lead's isotope profile to other samples from around the world, the researchers will be able to hone in on where the ship was built, or where it sailed from.

"One of the goals will be to virtually excavate and re-excavate the site in the computer afterwards."
Brendan Foley

Potentially, more of the bronze statues recovered on previous trips—hands, feet and other fragments have been found and are on display in the National Museum in Athens—could be identified through the metal heat map.

Finding more of the statues "would be quite a big contribution to art history and culture but we also expect that in amongst the fragments of the statues will be other amazing things. What kind of things? We can't even imagine. The possibilities are boundless. This ship sank carrying the finest material that was available in the entire eastern Mediterranean in the first century BC," Foley said.

Like the mechanism that it carried, the Antikythera is unique for its time period. Its hull planks are some of thickest seen in antiquity, indicating 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—some 1700 years after the Antikythera sailed.

Why was the Anitkythera so large? 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. The Antikythera, however, may have been built for a mix of business and pleasure.

One hypothesis is that the Antikythera may both have carried early tourists and freight, thanks to the huge bronze and marble statues it transported as cargo.

If the ship had to carry statues, some up to three meters tall, they'd have to be packed well to prevent damage in transit. It's been posited that sand or straw could be used as the packing material, but Foley suggests grain could be a more likely candidate: not only would the statues be protected but the grain could be sold on at the Antikythera's destination, making it a far more economical option.

"The ancient grain carriers weren't just cargo ships, they were more like RMS Titanic. They were more like luxury cruise liners," Foley said.

"The couple of extant literary references to grain carriers refer to these floating palaces: mosaic floors, libraries, and amazing cabins, well appointed for the passengers—the 200 or 300 passengers that could be aboard from Rome to Egypt or the Black Sea. They would be sort of the world's first tourists. As the ship was loaded up with grain, which could take a couple of months, they would tour around and then get back on the ship at the end of the season."

Any artefacts, such as mosaic pieces, would lend credence to the theory, but more evidence could come from the bones of passengers that died when the ship sank.

"There's other circumstantial evidence that points to this being the first grain carrier ever discovered, and that's the luxury goods that were carried onboard and also the presence of skeletal remains of a young woman," said Foley.

Remains of four people on the wreck have been found so far, and more may still be on the wreck. Should other bones be recovered, they will be subject to a vigorous recovery procedure to make sure there's no DNA cross-contamination between the dive workers and the bones themselves. All workers on the boat will give cheek swabs to make sure their genetic material can be identified if it ends up on the bones accidentally.

WHOI is now looking for a company that can work with it to analyse the DNA from the bones, perhaps hinting at where those on the ship—be they sailors, high-roller tourists, or slaves—originated from.

The WHOI scientists have already got a handle on other aspects of the travellers' lives, from their hygiene habits to their diets, thanks to the ceramic storage vessels found on the wreck site. The first Antikythera wreck has already yielded amphora, the "55 gallon drum of antiquity", table jugs known as lagynos, and unguentaria—the small bottles that would hold medicines, cosmetics or perfumes.

"With all of these types of ceramic artefacts, they're empty now, but we can take swabs and using police forensic techniques we can pull ancient trace DNA from the ceramic matrix of the original contents, down to the species level," Foley said.

It's not uncommon to find ancient ready meals in some of the jars—mixes of legumes or meats, herbs and spices—but the information from the jars can be far more valuable, giving an indication of what commodities were being traded between what locations, enabling archaeologists to get a better insight into the economy of a region than historical sources alone can provide.

"It's fun for us," said Foley, "because we feel like we've opened up a whole new vista on the past, and we can generate hard data on these early economies. What are they actually importing and exporting, what are they producing, what are they consuming? And it's all right there in these ostensibly empty jars."

Even traces of the ancient grain may still be hidden in the sands around the wrecks for those with the right tech to find it. While the grain is long gone, it will have decomposed to leave characteristic starches and structures called phytoliths, which can be detected with a powerful enough microscope.

WHOI's team returned to the wreck site in the summer of 2015 with their metallic heat maps to begin the process of finding out if the Antikythera has more secrets go give up.

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New robotic scuba exosuit acts like a mini submarine that helps humans stay longer in the deep sea.
Image: WHOI

"We're always analysing the data and updating the data, so this year, those wonderfully precise data from the maps produced by the robots, we'll have those on iPads. Those iPads will be in housings and we'll have interactive maps with us as we're diving on the site," Foley said.

The divers move through the water, iPad in hand, looking for the points of interest from the heat maps, and checking their position against those locations as they go. They carry handheld metal detectors too, to spot any metal artefacts buried under the seafloor surface, and are accompanied by professional photographers and videographers, as well as using the iPad cameras to gather snaps too.

"All those data at the end of the day are incorporated into the maps. In the best vision we have of this, we'll have have a data manager incorporating everything we're doing daily," said Foley. "One of the goals will be to virtually excavate and re-excavate the site in the computer afterwards, by using our series of images over the trench we're digging to be able to take it down and refill it in the computer afterwards, so we make sure we're absolutely documenting every action we take."

The divers use rebreathers to allow them to investigate the wrecks at depths that would normally prove fatal to humans in a matter of minutes. By keeping the gases they breath in and out inside a closed loop, adding oxygen where necessary and cleaning out the carbon dioxide, divers are able to spend a far longer time on site than they would be able to with conventional scuba gear.

"Putting humans in the water is always the option of last resort because we have to eat, we have to poop, 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.

That's why today's underwater excavations will typically rely heavily on robots. They can spend far longer underwater and go to far deeper depths than humans. However, often they're used as observers, with the most difficult work still done by humans.

Last year, WHOI experimented with a fusion of the two: an Iron Man-like exosuit. The exosuit is a small wearable submarine that keeps the diver's air at the same atmospheric pressure as it is in the water.

While the WHOI team didn't use the experimental suit for any work on the wreck site, it was tested out on the vicinity of the Antikythera, and the organisation is now considering whether to plough ahead with a development program.

"You can stay for hours and hours doing work or observing work, and then be winched right back up to the surface," said Foley. "You won't have to pay a decompression penalty. You just jump out of the suit and go have a cup of coffee."

Foley called the oragnisation's August 2015 diving and excavating trip "the most intensive period of activity on the Antikythera ever." The results of the landmark excavation are still being revealed.

LISTEN: Free audio story: The 2,000 year old computer that's rewriting human history

The HMS Erebus

The 19th century saw the birth of polar exploration, as maritime nations rushed to stake their claim on the unknown winter continents.

In 1845, two ships left Kent bound for the Arctic, tasked with being the first to navigate the Northwest Passage, a hoped-for trade route between Europe and Asia through the Arctic Ocean.

The ships never returned to England.

It's thought the two vessels, HMS Erebus and HMS Terror, were abandoned when they became icebound, leaving the crew to begin a trek on foot across Canada in the hope of finding supplies, or human settlements along the way. The crewmen never made it to safety, and subsequent investigations of remains, found over 100 years later, found traces of starvation, lead poisoning, scurvy, pneumonia, and cannibalism among the party.

The history of the Erebus and Terror has been built up piecemeal since the ships were lost, using testimony from local Inuit, the objects left behind by the crew on their desperate journey, and even notes written by the acting captains following the death of Sir John Franklin, the expedition's captain.

The Inuit reported seeing one of the ships go down off the coast of King William island in around 1850, and they would be the last humans to lay eyes on the vessels for the century and a half that followed.

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A Canadian team set out in 2015 to search for the HMS Terror.
Image: Thierry Boyer/Parks Canada

In 2008, Parks Canada, the Canadian Hydrographic Service, and the government of the Arctic territory of Nunavut began a fresh expedition to find the Erebus and the Terror—the latest in a long line of recovery missions that stretches back to Victorian times.

Over the years, the expedition had narrowed down its search to two areas, one in the Victoria Strait, another in Queen Maud Gulf, prompted by testimony from local Inuits who reported going aboard the vessel after its desertion by Franklin's men.

The Parks Canada returned every year, surveying the two areas for traces of the lost vessels. With ice making the areas inaccessible for much of the year, the archaeologists had only a handful of weeks at a time to hunt for the missing ships.

In 2011, the searchers drafted new technology to aid the search: aircraft equipped with lidar symmetry, which could scan the shore areas to a depth of around 20 meters. While the lidar systems weren't expected to be able to pick up signs of a wreck, they could help the team put together better maps of the region, which is still largely uncharted even today. The Canadian Space Agency also joined the project, providing satellite map data from the Radarsat I and II satellites, allowing the team to better delineate the shoreline and the low tide marks.

"Even the maps for the coastline of this area weren't terribly accurate. They were off by about 4km. if you're trying to steer a survey line and not run into an island, 4km is fairly significant," said Ryan Harris, who led the Parks Canada team. With better maps, the team could use side-scan sonar and multibeam echosounding, which can build up a picture of the seafloor, without risk of damage to the environment or to their equipment.

After what Harris describes as "six very long, monotonous years staring at the sonar waterfall display cascading down the screen, often for very, very long hours—sometimes 16 hours a day—bobbing around on the ocean, turning a little bit green as we concentrated on the data all the while," in September last year, an image loomed out of the sonar data.

A shipwreck.

The team knew had almost certainly found one of Franklin's ships. Due to its remoteness, very few ships have sunk in the region, and those that have are generally a matter of public record. Unless a whaling ship had made it up to the Queen Maud Gulf without being noticed, the team were likely to be the first people to see either the Erebus or the Terror in over 160 years.

The team changed its survey grid, aligning it with the axis of the ship, shortening the range of the sonar and boosting its resolution. The telltale details of the ship emerged.

"We could see, for example, a herringbone pattern of diagonally-laid upper decking, which is a laminate construction, sort of a second layer of decking laid over the first. It's absolutely typical of royal navy dockyard modifications for Arctic service," said Harris.

However, without any scuba gear on the survey boat, the first up close look went to a robot, the Saab SeaEye falconer remotely operated vehicle (ROV).

"That's when we saw the two brass six-pounder cannons," said Harris. "They were one of the first things we saw as we crept over the seafloor to the site. Everything was just so picture perfect. You couldn't have scripted it better, almost everything you looked at was just so remarkable."

"Out of the gloom on the seafloor loomed this stately shipwreck site, standing bolt upright... It was absolute exhilaration."
Ryan Harris

When the scuba gear arrived, human divers were able to see the site for the first time. A gale had stirred up sediment under the water, but a mix of luck and judgment allowed Harris and his divemate to find enter the water near a timber that Harris could follow "hand over hand" to the wreck proper.

"Out of the gloom on the seafloor loomed this stately shipwreck site, standing bolt upright. It was that phenomenal feeling of making contact with this icon of maritime history," said Harris. "It was absolute exhilaration."

While it's common for wrecks to be found broken and battered, much of the ship—later confirmed as the Erebus—was still intact. The weather deck, upper deck, and quarterdeck were all still identifiable, and although the upper deck had been ruptured by ice, the holes allowed the two Parks Canada divers to peer down into the rooms below. They saw a glass case bottle, a container of spirits reserved for officers, and examined the areas where the ordinary sailors bunked down and the mess table where they would have taken their meals.

The first dive also found the ship's bell, broken free from the belfry but otherwise undamaged, stamped with 1845—the date the two ships had set sail for the Arctic.

While the ice closed over the site and eventually put an end to explorations, the team were able to return to the Erebus in April 2012, carrying a new piece of equipment that would allow them to access the site even in winter.

Defence Research and Development Canada, the military's technology arm, lent the archaeologists a tool that uses a jet of hot water to cut through ice. Using DRDC's 'hot water knife', a two meter section of the ice was removed, allowing the divers to slip beneath the ice and onto the wreck site.

"The advantage of diving in the water is that because of the ice there's no waves," said Harris, "so all of the particulate settles down on the seafloor and you have a really, really good visibility. That's where we're able us to use different technological approaches to document the site that work a lot a better."

As well as documenting the outside of Erebus and its location, the Parks Canada team face the difficulty of navigating within the ship itself, mapping the location of the objects within it and any subtle associations with them.

The team uses stereophotogrammetry for that. Harris said, "It's an extremely important tool for us now. Essentially it uses a whole bunch of still photos, and software is able to determine the three dimensional relationship between subsequent exposures and produces a three dimensional model or a point cloud of what the camera saw, so in just a couple of hours you can aquire a whole bunch of data and produce three dimensional images of the entire wreck site."

The expedition is also experimenting with laser scanning, in partnership with Canadian firm 2G Robotics which makes underwater scanners normally used for detecting damage on oil pipelines. The company developed a longer range scanner for the Franklin expedition, which can map up to a five meter range with millimeter resolution, used to image the outside of the wreck. The expedition also used a smaller machine, with a range of between 50cm and 20cm, for investigating the interior, allowing the team to record the position of small objects, like plates, where they lay within the ship.

The team had another novel piece of technology at its disposal: a 7.5-meter autonomous underwater vehicle, the Arctic Explorer. Unlike the humans that operate it, it can stay underwater for 72 hours, and was packed with all sort of tech: inertial guidance systems and doppler velocity logs to plot the position and speed of the vehicle, as well as an interferometric synthetic aperture sonar (InSAS) system that can record a far wider swathe of radar (630 meters) than the towed side-scan sonar system the survey boat normally uses.

Said Harris, "It can resolve a target the size of your thumb anywhere in that sonar record, because it's using almost like synthetic aperture radar—it's using multiple radars and its synthesising that into one coherent very, very accurate image."

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Parks Canada's Ryan Harris points to the sonar image of the HMS Erebus.
Image: Theresa Nichols, Fisheries and Oceans Canada

Despite all its technical bells and whistles, the Arctic Explorer had to watch from the sidelines.

"We thought this was going to be the best technology to be used for underwater archaeology because we were hoping that the InSAS system would be able to detect very small, otherwise difficult-to-detect, cultural targets—detached rigging, rope lying on the seafloor, piece of iron plating lying flat on the bottom, any oars, or anything that might be difficult for us to detect with towed sonar," Harris said.

But it was thwarted when the team wanted to take it onto the two search sites last year. In the Victoria Strait search site, there was too much ice to deploy it; in the Queen Maud Gulf, the waters were too shallow for it to be used safely.

The technology may have been some of the best out there, but even it could be bested by Arctic conditions. It's a situation that Franklin and his men would have been familiar with.

Franklin's two ships were some of the first polar vessels to be equipped with steam engines—repurposed railway engines—leaving port with 12 days coal aboard, for example, as well as state-of-the-art Massey double action bilge pumps.

"I've never seen [the Massey pumps] in real life until we were face to face," said Harris. "At the time, that was the very best thing that the Royal Navy could lay their hands on, but the technologies at the time are so short lived because everything was changing so quickly."

The ships that were sent to find Erebus and Terror five years later had already had their bilge pumps upgraded to the newer Daunton model. Harris said, "Things were changing so very quickly in that sort of industrial period that this is like a snapshot of what things were like in 1845."

While Harris and his team continue to gain the Erebus' secrets and discover what other technologies she had onboard, the search will begin afresh for the Terror.

"We'll have five mulitbeam sonar systems pinging away at Victoria Strait trying to locate the second ship. That's important to do," Harris said. "The two ships together are a designated national historic site. To preserve them, protect them, and interpret them for the public, obviously we have know where both of them are. Their stories obviously are intrinsically intertwined, so we hope in the fullness of time to understand what happened to the expedition and find as many clues as possible, and both ships would certainly assist that."

The Mars

When the Mars sank in 1564, it was perhaps the biggest ship in the world—a fearsome vessel with over one hundred guns and 700 men onboard.

The Mars met its end in a bloody sea battle between Sweden, which had built the formidable warship, and the combined armies of Denmark and the German province of Lübeck. During the battle, the Mars caught fire but despite the clear danger, the Mars was still boarded in the last minutes above the waves by enemy forces. The flames ignited the gunpowder stored on the ship causing a huge explosion that blew out the stern of the ship and took her, and the men aboard her—the Swedish sailors and invading forces alike—to the bottom of the ocean.

While the Danish and German soldiers must have known the risks of a ship that was already alight, they still ventured aboard. Why? One suggestion was that they were desperate to recover the thousands of valuable silver and gold coins the ship was said to carry, even if it meant risking—and ultimately losing—their lives.

For over four hundred years, the wreck and its rumoured treasure had slept 75 meters beneath the Baltic Sea. Many attempts had been made to find her since her loss on the first day of the Battle of Öland. The one that was to prove successful, staged by a group of divers known as Ocean Discovery, had been 20 years in the making.

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The scientists were able to create a computer-generated 3D model of the Mars wreck.
Image: Ocean Discovery

Johan Rönnby, head of the MARIS research institute at Södertörn University set up to study the Mars, said, "Mars is a legendary ship in Sweden, and almost everybody wanted to find it. It was built by the King Erik the XIV, who was son of Gustav Vasa—Vasa is our Tudor dynasty. It's ship a connected to the building of Sweden. Sweden had become a country, and there was an attempt to make Sweden a European superpower and Mars was part of that concept, really. Erik had built maybe the biggest ship in the world in the 1560s, so Mars was a special ship. She was more than 60 meters long and very modern-equipped."

Ocean Discovery's divers had started their search decades ago, upgrading from echosounders to sidescan sonar in 1999. Due to the unreliability of the written sources of the time, the team had been investigating a relatively large area, 15 square miles, and had been hoping to zero in on the Mars using information from local fishermen on where their trawl nets had been caught on the seafloor—a sign that they might have become tangled in the wreck of the Mars.

The conditions in the Baltic Sea—the temperatures and absence of shipworm, which can destroy submerged timber—mean any ships that have sunk in its waters are often well preserved. Over the course of Ocean Discovery's search, the team had found tens of wrecked wooden ships maintained in a good state by the Baltic waters, located using the trawl snag data from the fishermen, but none had been the Mars.

Abandoning the historical data and information from fishermen, the team resorted to doing search passes over the area, dragging the sidescan sonar from east to west.

One day in 2011, the team had been tracking debris from a wreck site for some hours after finding some masts when something out of the ordinary loomed into view on its side scan sonar. "Halfway through, we found a wreck that looked like nothing else," Ingemar Lundgren said. A piece of the ship's hull 40 meters long had appeared, giving the first suggestion that the team had finally stumbled on the flagship of Swedish King Erik the XIV's fleet.

"The first indication [it was the Mars] was the size of the wreck. It was really, really huge on the sea bottom. We could see on the sidescan sonar pictures that this was a big, big wreck. when we saw the first pictures from it, we recognised the ship's [building] techniques... it was in many ways similar to the Mary Rose. Then we had a good indication it was very likely that it was Mars," Rönnby said. The Mary Rose, a 16th century English warship and the pearl of King Henry VIII's fleet, was sunk ten years before the Mars and salvaged thirty years before it.

"Mars is a legendary ship in Sweden, and almost everybody wanted to find it... There was an attempt to make Sweden a European superpower and Mars was part of that concept ... maybe the biggest ship in the world in the 1560s."
Johan Rönnby

A four man team—Richard Lundgren, Fredrik Skogh, Christoffer Modig, Anton Petersson—were on board the ship when it found the Mars, and sent a picture of the scan to Ingemar Lundren, who was processing images from the vessel onshore. "I said it could well be the Mars, because it looked so different."

It took some time to confirm the exact identity of the wreck after its initial discovery, however. "The sidescan sonar is the best technology available, but it's not so detailed that you can see cannon and things," said Lundgren. "It's more technology for locating, not for marine archaeological survey."

Having spotted the wreck, the team sent down an ROV for a closer look. "The camera quality on the ROV is quite poor. We did see the intact hull side but we didn't see any gun ports. We were filming for an hour but we didn't see any cannons. Navigating an ROV on a complex wreck site like that is hard. It's very three dimensional, there's wood sticking up, and the umbilical from the ROV can get tangled. The ROV surveying couldn't prove it was the Mars, it could only prove it was a large warship," Lundgren added.

Absolute confirmation would require human divers. A three-man team, comprised of the two Lundgren brothers and Skogh, went in to investigate.

As they swam over the wreck, gradually distinctive cannons began to appear: first just one, caught in the beam of a single diver's flashlight, then five, six, seven piled up on top of each other.

Still it was not enough to put the wreck's identity beyond doubt: another 16th century Swedish warship, the Svärdet, had sank in the same region as the Mars and not long after. Was it the Svärdet they had found?

Further dives in the weeks following after the discovery of the wreck were used to map the wreck's guns, and found that some bore the Vasa coat of arms. Locating a wrought-iron breech-loaded cannon, however, was enough to put the identity of the ship beyond doubt.

Having found the Mars after a two-decade search, Ocean Discovery found that they weren't the only wreckhunters who were in the region. Using a satellite system called AIS, which allows ships to know the location of nearby ships, Ocean Discovery could see a rival team from underwater survey business Marin Mätteknik (MMT) were also nearby and looking for the warship. In three or four days, they would be on top of the wreck before Ocean Discovery had had time to register the discovery as its own.

"We tried to distract them. We know they could follow us on AIS," Ingemar said, "so we set up a search pattern away from the wreck site and we made it look like we had found something. We stopped in one place and deployed an ROV. They took the bait and came over." Ocean Discovery had won enough time to confirm the identity of the Mars and record it with the authorities.

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The Mars expedition team also took it a step further and 3D printed the shipwreck to explore it even more.
Image: Ocean Discovery

The former rivals are now friends: Ocean Discovery, MMT, and the University of Södertörn formed a joint project to investigate the wreck.

Among the techniques used to research the Mars was photogrammetry: divers took hundreds of normal digital still photos of the site from many angles, which is then sewn together by photogrammetry software to create a two-dimensional map of the site.

"In 2012, we made a photo mosaic of the whole site with 600 pictures put together. It's at 70 meters depth, it's totally, totally dark in the Baltic Sea. It's a tricky case to work on. You need to take diving technology and rebreathers and a lot of lamps, of course," said Rönnby.

Thousands more photos have been added since, and divers will carry on adding more, thanks to funding from both National Geographic North European Fund and Waitt Institute.

Using sidescan sonar and multibeam sonar, the project began to build up a high-resolution three-dimensional picture of the wreck too.

Multibeam sonars can be either mounted on the underside of a ship or on an ROV and, by emitting sound waves and recording how long and from what direction they bounce off a surface and return, can build up a 3D picture of the sea floor.

Multibeam sonar, provided by MMT, gives highly accurate georeferencing, so archaeologists known where the wreck is and where each object can be found. The multibeam sonar and photogrammetry are used in concert. If an object located on a 2D image is worthy of further scrutiny, its location can be found using the multibeam, and a diver sent down to precisely the right place.

The project is also working with a BlueView sonar scanner from MMT, which when positioned on the seafloor can gather 60 million measurement points in 15 minutes. Combined with the million photos taken by divers, a map that's precise to two millimeters has been built up—higher resolution than the multibeam. In time, however, the BlueView point cloud will be merged with that from the multibeam sonar so the two technologies can fill in any gaps from each other.

Thanks to the photogrammetry, BlueView, and multibeam sonar imagery of the wreck, the Mars can now be explored in great detail without putting divers tens of meters down in the freezing Baltic.

"A lot of people have said to us, 'Oh, a new Vasa ship, how should we be able to pay for the conservation and everything?' and we said no, we're not going to do that, we're going to salvage as much information as possible from the wreck instead and leave it on the sea bottom. It's what we call the future of maritime archaeology to be able to do that. That has been an important part of the whole technology development to do that," Rönnby said.

Much of the coming archaeology of the Mars will be done on dry land, using a computer, rather than by divers. Due to the resolution of the 3D model—and the relative lack of sediment in the environment—archaeologists will be able to explore the wreck in fine-grained detail. Those that have already been exploring the photo mosaic have been doing so at their desks, looking for artefacts or other elements the divers may have missed.

Those dry-land archaeologists have managed to pinpoint much of the treasure, including thousands of those rumoured silver coins. "On the 3D photo we can zoom in and see the coins laying there all around the sea bottom," said Rönnby. "It looks like a chest exploded with silver coins."

Even the few bones around the wreck can give up their secrets without being moved. A PhD student is studying the 3D mosaic, finding out the physical characteristics of the person—their height, whether they had certain diseases—and even how they died by studying fractures or burns on the bones.

While two silver coins and a couple of cannon have been salvaged and brought to the surface with the help of an ROV, the plan is to leave as much of the wreck in situ, so the excavations won't ultimately affect the wreck in any destructive way. As well as images, the technology gathers the precise position of artefacts and other elements, so no need to pin out grids on the site either.

That's not to say that the Mars won't be seen above water in future, though. The detailed way the way the wreck has been mapped means that it can be brought to the surface in a new way: with 3D printing.

"It's fun for us, because we feel like we've opened up a whole new vista on the past."
Brendan Foley

"You can dive on the wreck from the computer, you can zoom into details, you can see artefacts, you can turn them around and then most fantastic thing you can do—you can even print them. You can print parts of the structures or you can print artefacts with 3D printers."

So far, a not-to-scale section of the hull and one of the guns have been printed out. In future, perhaps, museums around the world could take advantage of such techniques. Multiple museums could print out copies of the same object from the wreck, giving them to visitors to touch or academics to study, and not have to worry about how to maintain the right conditions for conservation. The imagery could equally be used to build a 3D visualisation that visitors could manipulate and explore themselves, putting themselves at the heart of history.

In the next few years, would-be marine archaeologists will have yet another way to explore the Mars without getting their feet wet: the hope is to create a virtual reality version of the wreck, that individuals can explore through an Oculus Rift headset.

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According to Rönnby, Mars offers "the possibility to come so close to the middle of battle."

"A lot of ships timbers are still black and you can see the explosion," he said. "There are guns still sitting in wood, and cannonballs have penetrated into the hull. You are really close to the battlefield. In the end, that's what I think is the purpose of archaeology is: to study general things about humans, in this case, why we are fighting, how we fight, and how people behave in war situations. I would like to use Mars as part of a general humanistic discussion about warfare and people in war."

Cover photo credit: Kirill Egorov, MARS 2015

About

Jo Best has been covering IT for the best part of a decade for publications including silicon.com, Guardian Government Computing and ZDNet in both London and Sydney.