After days of searching for the submersible that went missing in the Atlantic Ocean as it transported five people to view the wreckage of the Titanic, officials said its fate is no longer a mystery: it imploded in the depths of the sea, apparently within hours after starting its descent. 

Coast Guard Rear Adm.John Mauger said at a news conference Thursday that teams had found pieces of the missing sub "consistent with a catastrophic implosion of the vessel" in a debris field on the sea floor, just 16,000 feet from the bow of the Titanic. 

A U.S. Navy official said the military detected "an acoustic anomaly consistent with an implosion" on Sunday — shortly after the sub, called the Titan, lost contact with the surface, CBS News national security correspondent David Martin reported. 

But search and rescue teams did not want to give up hope, and used the information to help narrow down the search area. 

What happens during an underwater implosion?

Implosions happen when objects are under significant pressure. Will Kohnen, chairman of the professional group the Marine Technology Society Submarine Committee, told Reuters that when it comes to an undersea implosion, "in a fraction of a second, it's gone." He believes the implosion likely happened "fairly early on" into the sub's venture.

"It implodes inwards in a matter of a thousandth of a second," he said. "And it's probably a mercy, because that was probably a kinder end than the unbelievably difficult situation of being four days in a cold, dark and confined space. So, this would have happened very quickly. I don't think anybody even had the time to realize what happened." 

For Kohnen, a puzzling aspect of the situation was how communication and tracking were lost so soon. 

"It's all acoustic, but you have a system for voice, you have a system for a text ... range finding ... sonar, and it's based so that you have backup, so that not everything fails at the same time all of a sudden," he said. "...It was curious that all the systems stopped at the same time." 

An implosion, he said, "indicates that would have happened on the way down, early in the dive." 

How deep was the Titanic submersible when it imploded?

Mauger said Thursday that it's still too early to tell when exactly the vessel imploded. But what officials do know is that lost contact with its mothership an hour and 45 minutes after it went under the Atlantic. 

And how much pressure the carbon fiber hulled submersible was under when it imploded would depend on how deep it was at the time. When standing at sea level, there are 14.7 pounds of pressure pressing down on the human body per square inch, according to NOAA. But that pressure changes drastically as you descend deeper and deeper underwater — often noticeable among divers who feel the pressure in their masks and ears. 

"The deeper you go under the sea, the greater the pressure of the water pushing down on you," NOAA says. "For every 33 feet (10.06 meters) you go down, the pressure increases by one atmosphere."

The remains of the Titanic are at around 12,500 feet down, meaning that the pressure at that depth would be about 400 times the pressure you would feel at sea level — far beyond what the human body could withstand for even a moment. Scientific American reports that at such depths, "every square inch of an object's surface experiences the equivalent of 5,500 pounds of force."

Five people were aboard the lost submersible: British businessman Hamish Harding; Pakistani-British businessman Shahzada Dawood and his teenage son, Sulemanl French explorer Paul-Henri Nargeolet; and Stockton Rush, the CEO of OceanGate, the company that offered the tour of the Titanic's wreckage. 

The Coast Guard is leading the investigation into the incident, and the National Transportation Safety Board said Friday it will assist. 

In:
• RMS Titanic
• Submarine
• Navy
• Atlantic Ocean
• Submersible

Li Cohen is a social media producer and trending content writer for CBS News.