Amazon founder Jeff Bezos says he has located the long-submerged F-1 engines that blasted the Apollo 11 Moon mission into space.
In a blog post, Mr Bezos said the five engines were found using advanced sonar scanning some 14,000ft (4,300m) below the Atlantic Ocean's surface.
Mr Bezos, a billionaire bookseller and space-flight enthusiast, said he was making plans to raise one or more.
Apollo 11 carried astronauts on the first Moon landing mission in 1969.
The F-1 engines were used on the giant Saturn V rocket that carried the Apollo landing module out of the Earth's atmosphere and towards the Moon.
They burned for just a few minutes before separating from the second stage module and falling to Earth somewhere in the Atlantic.
Mr Bezos' announcement comes days after film director James Cameron succeeded in his own deep-sea expedition, reaching the bottom of the Mariana Trench, the deepest point on the planet.
Although some F-1 engines remain, those from Apollo 11 do not Announcing the discovery on his Bezos Expeditions website, Mr Bezos described the F-1 as a "modern wonder" that boasted 32 million horsepower and burned 6,000lb (2,720kg) of rocket-grade kerosene and liquid oxygen every second.
"I was five years old when I watched Apollo 11 unfold on television, and without any doubt it was a big contributor to my passions for science, engineering, and exploration," he wrote, confirming that his team had located the engines but without hinting where they might be.
"We don't know yet what condition these engines might be in - they hit the ocean at high velocity and have been in salt water for more than 40 years. On the other hand, they're made of tough stuff, so we'll see," Mr Bezos wrote.
His privately funded team was planning to raise one or more engines, he wrote.
He said he planned to ask Nasa - which still owns the rockets - for permission to display one in the Museum of Flight in his home city of Seattle.
Nasa said it looked forward to hearing more about the recovery, the Associated Press reports.
Other elements of the Apollo missions - including the Apollo 11 command module - are on display in the Smithsonian National Air and Space Museum in Washington DC.
The attempt to raise the F-1 engines is not the first foray into space technology for Mr Bezos.
In 2000 he founded a private space flight firm, Blue Origin, which has received Nasa funding and is working on making sub-orbital space flight commercially available.