Missing aviator Amelia Earhart's 'plane' turns out to be 'just a pile of rocks'

The disappearance of pioneering aviator Amelia Earhart more than 87 years ago has remained one of the most captivating mysteries in history, with a handful of explorers devoted to scouring the seas for any clue to her final whereabouts.

Sonar imagery captured in January revealed a plane-shaped anomaly on the seafloor about 161km from the Pacific Ocean's Howland Island - the next location where Earhart was expected to land before she was declared lost at sea. The detection renewed a worldwide interest in the mystery and left many questioning whether Earhart's missing Lockheed 10-E Electra had finally been found.

After returning to the site on November 1, Deep Sea Vision - an ocean exploration company based in Charleston, South Carolina, that captured the original sonar image - has identified the object to be a natural rock formation.

"Talk about the cruellest formation ever created by nature," said Tony Romeo, the company's CEO, a pilot and former US Air Force intelligence officer. "It's almost like somebody did set those rocks out in this nice little pattern of her plane, just to mess with somebody out there looking for her."

Romeo said he was surprised the object wasn't at least a different plane or a man-made object.

"We didn't pop any champagne bottles on the first time around, because we wanted to be 100 percent sure, (but) there was a somber moment," Romeo told CNN in a phone call. "I think everyone just kind of took a little bit of time, little space, and then we recollected ourselves … and we got right back to work on searching some new areas that we wanted to search."

Deep Sea Vision announced the update in an Instagram post on 6 November, saying its search continues. After discovering the rock formation, the expedition crew explored more than 2590 square kilometres for a search total of at least 19,943 square kilometres of ocean, Romeo said.

While it was not the update the team expected, Romeo and other experts said that hope shouldn't be lost for finding closure one day for the aviation legend.

The hunt for Earhart's plane continues

The rock formation was more than 4877 metres underwater. Upon first discovery, the team's advanced autonomous underwater vehicle, or AUV, a device that maps the seabed using sonar technology, was about 500 metres away, Romeo said.

The team sent out the AUV directly above the site in early November, producing a high-resolution image of the rock formation.

"The mood was very jubilant on the way out," Romeo said. "We were excited [but] cautiously optimistic because we knew there was a possibility that [the anomaly] may not be what we thought it was, but obviously everybody was excited."

It was a long wait for the AUV to get into position to scan the object - about 24 hours from launch until the team could see the data, Romeo said. After the anxious wait, the image surprisingly revealed that the object was a natural rock formation, he said.

Romeo said other images further confirmed the rock formation, but the company is not yet releasing any material other than one sonar image, as a documentary on the expedition is in the works. The team may not return to the area to search farther until 2026, due to other missions, Romeo said. "It'll be some time before we get back out there," he added, "but we want to find it, and I believe we will."

Meanwhile, other explorers are continuing their search, such as Nauticos, a deep ocean exploration company based in Kennebunkport, Maine, that has conducted operations for the lost aircraft in the past. Nauticos recently finished an analysis of what it believes to be high-probability areas for where the plane could be found based on radio data, and the remaining area left to be searched could possibly be covered in one more expedition, said David Jourdan, cofounder and president of Nauticos.

When Deep Sea Vision first announced the anomaly, Jourdan cautioned against using sonar imagery to identify anything on the seafloor.

"On our website, we say, 'Long range sonar images have historically proven to be deceiving, especially in areas with geological formations.' That's a polite way of saying it could be just a pile of rocks. … Which turns out to be the case," Jourdan said recently in an email.

Finding objects on the seafloor is like "searching for a contact lens on a football field in the dark using a penlight for illumination. It can be done, but it takes careful, methodical work," he added. "The quality of the sonar data is important, as is keeping track of where you searched and not missing any spots along the way."

Earhart's mysterious disappearance

Conspiracy theories have developed since the aviator's disappearance, but the US government suspects that Earhart and her navigator crashed into the Pacific when the plane ran out of fuel.

Earhart and navigator Fred Noonan took off from Lae, Papua New Guinea, on 2 July, 1937. The aviator's last radio transmissions grew stronger as she got closer to Howland Island, indicating she was nearing it before she disappeared, according to Dorothy Cochrane, a curator for general aviation in the aeronautics department of the Smithsonian National Air and Space Museum. The pair was declared lost at sea after the US government conducted a 16-day search.

Cochrane said she was not surprised at the setback in the hunt for Earhart's plane. "I'd like to hope that they can find it, just to put it all to rest. But in reality, it's a big ask. It really is a difficult thing to do," she said.

"It is one of the greatest unsolved mysteries ever, I used to say back in the day of the 20th century. Now we're well into the 21st century. There was no one who had the cachet of an Earhart, [who] was being followed worldwide at the time and making such dramatic flights."

Romeo said he believes the search will only get easier as technology advances.

"In some ways, I'm even more excited now about it, right? It was like the plot thickens, and the riddle is still unsolved… I hope this inspires other people to maybe go look for her or at least learn about her and her story," he said. "I want to see the plane found. She's out there. She didn't just disappear into thin air."

- CNN