On December 1, 2020, one of the world’s most iconic astronomical facilities came crashing down. The Arecibo Observatory in Puerto Rico, with its 900-ton platform and massive dish, was a symbol of scientific exploration, tracking distant exoplanets and searching for extraterrestrial life.

But its collapse wasn’t the sudden disaster we’ve been made to think. A recently released report by the National Academies of Sciences, Engineering, and Medicine has revealed a slow, preventable failure that was years in the making.

Unheeded Warnings

In 2017, Hurricane Maria delivered a devastating blow to Puerto Rico. And Arecibo, perched on the island’s northern coast, bore the brunt of the storm. Winds exceeding 100 mph battered the facility, exposing weaknesses that would prove fatal. The damage caused by the hurricane started a chain of events, including what engineers describe as “zinc creep” — a previously undocumented phenomenon that ultimately brought the telescope down.

The cables holding up Arecibo’s 900-ton platform began slipping from their sockets in the years following the hurricane. Inspections recorded the slippage but contracted external engineers and consultants did not flag it as a serious threat. “The lack of documented concern . . . is alarming,” the report stated.

This oversight, compounded by the facility’s aging structure and missed opportunities for maintenance, set the stage for Arecibo’s collapse.

The first major warning came in August 2020 when an auxiliary cable failed. Then, in November, a main cable snapped. By then, it was clear the platform couldn’t be safely repaired. But before officials could proceed with its decommissioning, another auxiliary cable gave way. And the structure collapsed. It took less than 10 seconds to destroy what had been 57 years of groundbreaking scientific work.

A Complex Failure That Caught Everyone Off Guard

The investigation into the collapse of Arecibo, operated by the National Science Foundation (NSF), has been described as one of the most baffling in modern engineering. At the heart of the issue were the zinc spelter sockets. These essential components anchor steel cables by filling them with molten zinc, which hardens around the wires. It’s a method that has worked for more than a century since the technique was invented. But at Arecibo, this process failed.

The report suggests that the high levels of electromagnetic radiation from the observatory’s powerful radio transmitter may have contributed to the zinc’s failure, a phenomenon called electroplasticity.

“It opens up opportunities for exploiting it for beneficial uses as well,” Habib Tabatabai, a structural engineer on the committee, told Astronomy. In this case, however, the interaction between the radio waves and the material likely sped up its decay.

Zinc creep, the gradual deformation of the material, had not been observed at other facilities. So, no structural engineers had anticipated it. The discovery of this behavior at Arecibo means engineers must now consider the possibility of similar failures in other structures that use zinc spelter sockets.

A Tragic End, a New Beginning?

While Hurricane Maria triggered the collapse sequence, the ultimate cause was much more complex. The ‘sudden’ collapse of Arecibo wasn’t sudden at all as the researchers found that the “failure sequence” traced to 39 months before the event.

“The lack of documented concern from the contracted engineers about the inconsequentiality of cable pullouts or the safety factors between Hurricane Maria in 2017 and the failure is alarming,” the committee wrote.

The report concludes that with proper maintenance and a faster response to the signs of cable slippage, Arecibo might have been saved — at least for a while.

“Absent Maria, the committee believes the telescope would still be standing today but might have eventually collapsed if its unique, accelerated zinc creep had not been addressed before it was decommissioned,” the report says.

But by the time Arecibo’s structural issues came to light, it was too late. Funding for repairs had been delayed, and the structural problems were misunderstood. “None of the proposed repairs would have saved the Arecibo Telescope from collapse,” the report concludes.

Now, the site is slated for a new chapter. The National Science Foundation plans to transform the site of the observatory into an education center focused on STEM disciplines, though the opening has been delayed until 2025. The new center will honor Arecibo’s legacy while ensuring that future generations learn from its groundbreaking discoveries — and its tragic fall.

As engineers continue to study Arecibo’s collapse, they hope that what they learn will not only prevent similar failures but also open new possibilities for the future of materials science and structural engineering.

“It’s an opportunity to improve understanding,” Tabatabai said. For now, the radio silence over Arecibo is a stark reminder of what disasters await when some signals are missed.