It's been 44 years since humans first set foot on the moon, but less than one year since the first human to do so died. The passing of Apollo 11 commander Neil Armstrong, the best-known moonwalker, could herald a shift in how the past and the future of moon exploration is viewed.
"Actuarially, it's getting more likely that we're returning to a situation I never thought I'd see, with no living people on Earth who have ever been to the moon," said NBC News space analyst James Oberg.
The age of the moonwalkers began on July 20, 1969, when Armstrong and crewmate Buzz Aldrin took humanity's first small steps on the lunar surface. Since then, four of the 12 men who walked on the moon have passed away. The youngest of those who remain — Apollo 16's Charlie Duke — is 77.
Some of the Apollo astronauts have become outspoken advocates for specific visions of space exploration. Like Armstrong, Apollo 17 commander Gene Cernan has spoken repeatedly in favor of going back to the moon. Earlier this year, Armstrong's Apollo 11 crewmate, Buzz Aldrin, came out with "Mission to Mars," a book laying out his vision for Red Planet exploration. Meanwhile, Apollo 9's Rusty Schweickart is a leading proponent of asteroid missions.
Does all that advocacy have an effect? And will it be missed when it's gone?
"None of those policy questions, I think, are decided on the basis of the advocacy of one group of people, the astronauts or anybody else," Roger Launius, a space historian at the Smithsonian Institution, told NBC News. "The astronauts have a strong voice, there's no doubt about that. And when they speak, they have a credibility that the average person just doesn't have. But in the end, they don't make the decision."
Launius said the eventual fading of the moon generation is likely to bring a subtler change in historical perspective, just as the passage of the last World War I veterans shifted our view of that conflict.
"They have this ability to speak with authority about the eyewitness aspects of this effort, and no one else can do that," he said. "It's not that the event is less significant because there are no eyewitnesses, but our perspectives obviously shift a bit."
Moon-hoax theories fading
Today, fresh perspectives on the moon are coming from robotic probes such as NASA's Lunar Reconnaissance Orbiter, which captured images of the Apollo landing sites. Such images, released over the past couple of years, have put claims that the moon landings were faked to rest for all but the most hard-core conspiracy theorists.
In retrospect, it's understandable that some people would have doubts about the TV broadcasts and pictures from the moon. Some of the phenomena seen on the screen — such as the seemingly starless sky, or the flag that waved in the vacuum of outer space — really did look otherworldly, Oberg said.
"The lighting and the shadowingwere wrong ... for Earth," he said. "They weren't flaky objections. You just have to realize that the astronauts 'weren't in Kansas anymore.'"
Going back to the moon
When will humans go back to the moon? NASA's current policy focuses on sending astronauts to study a piece of an asteroid, and eventually explore Mars and its moons. The exploration of Earth's moon would be left primarily to the private sector and international efforts.
The Golden Spike Company is working on a launch system that could get two spacefliers to the moon and back in the 2020s for an estimated $1.4 billion. The company has scheduled a workshop in October to lay out the opportunities for potential customers.
Oberg is betting that someone will eventually find a way to take advantage of a "secret back door" to the moon's surface: a space elevator system that could grab a payload or a passenger spaceship from lunar orbit and pull it down on a skyhook. Experts have been kicking around the idea for decades, and Oberg himself referred to the skyhook system almost four years ago. He's just waiting for someone to pick up on the idea.
"The moon is the ideal place in the solar system for a rotating skyhook," Oberg said.
What's your perspective on the past and future of lunar exploration? James Oberg and I will discuss the legacy of Apollo 11 on "Virtually Speaking Science," an hour-long show that airs on BlogTalkRadio on the Web and in the Exploratorium's Second Life virtual auditorium. You can ask questions via Second Life,Internet Relay Chat or Twitter (use the #askVS hashtag). If you miss the live show, catch up with the podcast on BlogTalkRadio or iTunes. Here are previous episodes from "Virtually Speaking Science":
- SETI Institute's Seth Shostak on aliens in the movies
- Brian Switek on dinosaur fact and fiction
- George Djorgovski on the Internet and education
- Doug Griffith and Taber MacCallum on moon and Mars trips
- Sean Carroll and Matt Strassler on physics' X Files
- Ig Nobel's Marc Abrahams on weird science in 2012
- Paul Doherty on Curiosity and the year in science
- Shawn Lawrence Otto on climate change and the 2012 election
- Sean Carroll on what lies beyond the Higgs boson
- Alan Stern on the Uwingu mystery space venture
- George Djorgovski on the future of immersive virtual reality
- JPL's Dave Beaty previews Curiosity's mission on Mars
- SETI Institute's Seth Shostak about aliens and UFOs
- Paul Doherty on solar eclipses and the transit of Venus
- Veronica Ann Zabala-Aliberto on spaceflight and Yuri's Night
- JPL's Dave Beaty on the search for life on Mars
- Shawn Lawrence Otto on science and politics
- Ig Nobel impresario Marc Abrahams on silly science in 2011
- Rocket scientist Robert Zubrin on Mars exploration
- Propulsion expert Marc Millis on interstellar spaceflight
- Sean Carroll on the puzzles facing physicists
- Rand Simberg on the private-enterprise vision for spaceflight
- Martin Hoffert on the future of energy policy
- George Djorgovski on science in virtual worlds
- Alan Stern on suborbital research and NASA's mission to Pluto
- Col. 'Coyote' Smith on the outlook for space solar power
- Tim Pickens on rocket ventures and the Google Lunar X Prize
Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the NBC News Science Facebook page, following @b0yle on Twitter and adding +Alan Boyle to your Google+ circles. To keep up with NBCNews.com's stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.