By Agence France-Presse

Americans were celebrating the 50th anniversary of the first Moon landing on Saturday, a generation-defining event watched by half a billion people globally, as the US seeks to pivot to a new era of crewed space exploration.

At 4:18pm ET (2018 GMT) on July 20, 1969, the lunar module carrying astronauts Neil Armstrong and Buzz Aldrin touched down on the Sea of Tranquility, following a four-day journey.

NASA replayed online the CBS broadcast that was seen around the world.

“Houston, Tranquility Base here. The Eagle has landed,” Armstrong said.

A little over six hours later, at 10:56pm ET (0256 GMT Sunday), Armstrong placed his left foot on the Moon’s surface, and said: “That’s one small step for man, one giant leap for mankind.”

NASA has been in overdrive for several weeks to mark the anniversary, with exhibits and events around the country, including projecting the giant Saturn V rocket and clips from the mission on the Washington Monument.

“Looking back, landing on the moon wasn’t just our job, it was a historic opportunity to prove to the world America’s can-do spirit,” Aldrin, 89, tweeted Saturday.

Vice President Mike Pence delivered a speech from Cape Canaveral Saturday, from where Armstrong, Aldrin and Michael Collins, the third crew member, took off.

All three men were born in 1930, and Armstrong died in 2012.

“Today our nation pays tribute to three brave astronauts who sat atop a 360-foot rocket that lifted off from Pad 39A 50 years ago this week,” Pence said, joined by Aldrin.

“Apollo 11 is the only event in the 20th century that stands a chance of being widely remembered in the 30th century,” he added.

The anniversary has also revived a discussion about the future of space flight.

NASA has declared its intention to return to the Moon by 2024 under the Artemis program — the twin sister of Apollo in Greek mythology — and this time place the first woman on its surface.

It plans to establish a lunar orbiting platform, called a “Gateway,” studying how living organisms react to the radiation and microgravity of a deep space environment over a long period, as it looks ahead to a crewed Mars mission in the 2030s.

Experts doubt that the space agency can meet its current goals on time. None of the key elements — the rocket, crew capsule, lander, or orbital station, are yet ready.

Pence used the occasion to announce that the Orion crew capsule had now been assembled, “a critical milestone.”

According to a release by maker Lockheed Martin, it needs several months more of testing before it is delivered for launch processing in early 2020.

– ‘I’ve been there!’ –

In an interview with Fox News Friday night, Aldrin lamented the lack of progress in human space exploration since the Apollo program, which ended in 1972.

He also called for global cooperation to achieve humanity’s next steps on the Moon and Mars.

“It would not be at all helpful to be competing for the Moon or Mars, that’s very wasteful,” he said.

Collins too is keen to return to space sooner rather than later, and has advocated for the US to go “direct to Mars” rather than returning to the Moon first.

Asked on Saturday if he thinks much about the events of 50 years ago, he told Fox News: “Not very often.

“I lead a quiet life. I’ll be walking along down my street at night, when it’s starting to get dark and I sense something over my right shoulder and I look up and see that little silver sliver up there and think, ‘Oh that’s the Moon! I’ve been there!’

“It takes me by surprise.”

– Uncertain future –

In Houston, thousands of space enthusiasts descended upon the visitor area of the NASA Johnson Space Center, where military personnel put on a parachute display and held musical performances.

“I got to actually go out to the launchpad … and got to see when it blasted off,” said Darla Van Dyke. “So I have a lot of great memories.”

The White House meanwhile issued a statement announcing it was “committed to reestablishing our Nation’s dominance and leadership in space for centuries to come.”

But Trump is not the first president to make such promises: 30 years ago today, in 1989, the late president George HW Bush pledged to create a permanent base on the Moon and then send a crewed mission to Mars.

His son, president George W Bush, vowed the same in 2004 — but their ambitions came up short against budgetary realities.

The future of Artemis rests therefore on the willingness of Congress to substantially increase NASA’s current budget of $21 billion — and possibly on the outcome of the 2020 presidential election.