When Gerald Schaber and "Red" Bailey (his ginger hair now white) introduce me to the place they called home in the 60s, I feel bad I can't match their enthusiasm. We're standing at the edge of Cinder Lake, a massive volcanic field near Flagstaff, Arizona. The landscape is bleak and uninspiring. Black basalt stretches for miles.
It was here the pair spent almost a decade after they found themselves at the heart of the Apollo 11 mission, employed by the US Geological Survey in Flagstaff. It was here they donned spacesuits one summer – Nasa even supplied the oxygen – and sweated so much they lost 10 pounds each. They also tested jet packs and raced lunar vehicles. This was their moon.
"Creating the moon," Red says in his typical self-deprecating manner, "was my chore." I ask why he was chosen for that task. "I was good at bossing people around," he says, smiling.
He was also good with explosives. Armed with dynamite and lunar maps he blasted 143 craters with diameters ranging from 5 to 58 feet. We stand at the edge of one of them. It's shallow now but still impressive. Red pulls out a photo of the surface of the moon and one of Cinder Lake after the explosions – the pictures are identical.
He carried out "location tests" before Neil and Buzz arrived, asking fellow geologists, secretaries and warehouse staff to stand in as space explorers. "We drove them to a spot, gave them a photo of the moon and asked them to tell us where they were. The secretaries did best."
His and Gerald's main task was to teach Armstrong and Aldrin geology. The astronauts were enthusiastic pupils, keen to make sure their mission was worth something scientifically – an attitude Gerald feels wasn't always shared by Nasa. "To get Nasa's approval, even for a simple geology hammer, was a big job for us. They thought the astronauts might hurt themselves or puncture their spacesuits or something."
As we trek across the basalt our conversation turns to the "grover", or geological rover – the lunar vehicle the geologists came up with when the astronauts criticised Nasa's lack of scientific ambition.
In the end it wasn't used by the Apollo 11 team, but it has remained a source of pride. Today it sits in the foyer of the US Geological Survey building, looking dated and rather makeshift with its assortment of aviation dials and liberal use of tin foil. It ran on car batteries that lasted a mere 20 minutes, so the geologists had to follow behind with spares. Training sessions included numerous coffee breaks.
The men, now firm friends, were also asked to play their part at mission control on the day in 1969 when Apollo 11 finally landed on the moon for real.
Gerald describes how he was put in charge of monitoring Armstrong's heartbeat as the astronaut piloted the Eagle down to the lunar surface, missing the planned landing site and running perilously low on fuel.
"It was really slow on the way down," he says, "while Aldrin's was racing. But that was typical of Neil. Just like the first thing he really said was, 'Houston we have engine shut down here,' really calmly. Mission control told him to he speak again. It was then he said, 'The eagle has landed,' for the TV networks. He was just that cool."
He sounds starstruck. He confesses he was. "OK, I got his autograph. I asked him when he got out of isolation and was chastised [by his boss] for doing that!"
The pair speak of cold shivers, sitting in awe, being part of history. But the geology was their main concern. "The astronauts had time to plant the flag, time to salute, time to talk to the president of the United States," Red says, "but time was so short. All we wanted was for them to grab all the rocks they could."
"It's because we wanted to learn everything we could about the moon," Gerald says, "and every rock tells a story."
Finally I get a sense of how even Cinder Lake can excite them.
Karen Bowerman is a writer and TV presenter. She was formerly the BBC's consumer affairs correspondent and now shoots and presents films for BBC World's travel department