Ronald Evans / NASA file Earth rises above the moon's Ritz Crater in a view captured on Dec. 14, 1972, by Apollo 17's Ronald Evans.





Forty years ago today, human beings took their last steps on the moon, and had their last look at Earth framed by the lunar horizon. There have been other pictures from the moon since then, of course, but they've all been seen secondhand, based on data sent back by robotic probes. No humans have seen an Earthrise like this one with their own eyes since Apollo 17's crew began their homeward journey on Dec. 14, 1972.

For Andrew Chaikin — author of "A Man on the Moon," the definitive history of the Apollo moon effort — the 40th anniversary of our lunar farewell is a cause for reflection.

When Chaikin was a 16-year-old outer-space fanatic, he attended Apollo 17's night launch at Kennedy Space Center, thanks to a letter he wrote to his congressman asking for a VIP pass. "It was the only part of 'Man on the Moon' that I wrote from personal experience," he told me.

Chaikin said the 12-day mission ended the Apollo program "on the highest note possible."

"By the time of Apollo 17, those guys — not just the astronauts, but the flight controllers and the planners, the whole team — they were really on top of their game," Chaikin said. "It was a spectacular mission scientifically. They landed in an absolutely spectacular place. They took some of the most memorable photographs of all the Apollo missions."

Today, Chaikin posted a video that sums up the significance of Apollo 17 as well as the importance of keeping the moon on our agenda for exploration. The five-minute clip includes an amazing view of the lunar module's ascent module rising into the sky, transmitted from a remote-control video camera that was left on the moon's surface.

Chaikin hopes that astronauts will follow through on the implied promise in the words that Apollo 17 commander Gene Cernan spoke just before climbing up from the lunar surface: "We leave as we came and, God willing, as we shall return, with peace and hope for all mankind," Cernan said.

Five days later, Cernan and his two crewmates, Harrison Schmitt and Ronald Evans, rode their command module through Earth's atmosphere and splashed down safely in the Pacific Ocean — marking the end of NASA's last round trip to the moon. Most Americans weren't even alive when that happened. So how many people living today will still be around when the next moonwalk takes place?

"I don't think we realize how exciting it's going to be when we can see the moon rise, knowing that people are living there, working to make humans a multiplanet species," Chaikin says in the video. "And when they come home, they can share with us one of the moon's most precious gifts: the sight of the earth, breathtakingly beautiful as an oasis of life in the void."

To mark the 40th anniversary of the last human footsteps on the moon, "Man on the Moon" author Andrew Chaikin looks back at Apollo 17's explorations and explains why he believes the moon is the solar system's "jewel in the crown," beckoning us to return. Watch on YouTube

Today's anniversary, recalling our species' grandest voyages, comes amid a shocking episode in Connecticut that highlights our species' violent tendencies. It was that way for the Aurora theater shootings as well, which took place on the anniversary of the Apollo 11 moon landing. Will there ever come a time when the brighter side of our nature, exemplified by the peaceful Apollo program, finally wins out over the dark side? That's one more thing to reflect on over the weekend...

Here are some of your own reflections, selected from the comments you've left over the past week on earlier installments of our Apollo 17 coverage:

Astropreneur:

"December of 2022 isn't that far away. At the rate we are going, and with the uncertainty and lack of focus we are experiencing regarding our manned space exploration program, I'm afraid the 50th anniversary of the Apollo 17 mission will pass without any new footprints having been made on the moon's surface by American astronauts. "How would our lives be today if after 20 or 30 flights the Wright brothers dismantled their airplane and no one else flew for the next 50 years? "Are we any better off now for not having continued our manned flights to the moon, and perhaps beyond? "Will we sleep forever? America must awaken or we will find ourselves trailing behind the new leaders who will pick up the torch we long ago dropped. "Awaken, American spirit of exploration! Arise as you once did so long ago! I miss you."

Elizabeth-1372999:

"That flight stood out, like the first flight to the moon. I can remember some of the highlights: a geologist looking at rocks, giving a reason to go to space beyond the Cold War; the 'blue marble' and a reminder that we are the one habitable planet in the solar system, so we had better keep this planet healthy. The 'Merry Merry Month of December' was funny, but at the time, also a little bit of concern: There was a worry that the breathing apparatus had a problem. What made him sing was the low gravity; he found it fun to skip on the moon because each jump covered a lot of distance, and that was visible on television (something the moonshot deniers should notice). "I don't think of them as the last astronauts on the moon, but the most recent. It was a shock when my daughter saw videos of Neil Armstrong's moon landing in school, and I realized that another moon landing had not happened in her life. She is much older now, and my grandson has never seen a moon landing, and more and more funding is being cut, even though information from the space program is still coming to us. Look at the information from the asteroid projects and the xenon rocket. The space program is such a small part of our budget as is. It seems that every time budgets are cut, the space program suffers, schools suffer, and children have less and less to feel proud of."

Rick Carter:

"The next step for mankind is to become a celestial being. Short of that, mankind is destined to become just become one more extinct species in the vast cosmos. It is only by moving out into that vast cosmos that we see a true reflection of ourselves."

FarmerJeani:

"In 1969, I sat in my sister's living room with my grandmother and watched Neil Armstrong walk on the moon. My grandmother reminisced about her life as we watched. Her father took part in the run for Indian Territory in Oklahoma. She and her siblings stayed with relatives in St. Louis while her parents built a cabin to house them. She liked to stand in the window and watch the lamplighter come around with his horse and buggy to light the gas street lights. She was educated on the farm by an old Cherokee woman who had been to finishing school in Europe, but forced on the long 'trail of tears' march to Indian Territory in 1838-39. She lost all of her family on the way. My great-grandfather eventually sold the farm and bought a store in town. Grandma married a farmer and moved back to Indian Territory, where she raised nine children without the benefit of electricity. All their water was carried from the creek, light was provided by kerosene lanterns and homemade candles. My children, grandchildren and great-grandchildren can never fully appreciate the grandeur of the moment as seen through my grandmother's eyes. It was an epic accomplishment and I have no doubt that we will return — to the moon and to many other worlds."

Bbbbmer:

"We truly are a great nation at times — if only we'd remember that."

Troy-2251798:

"My fear is that, in this day and age, America will go to the moon (and/or Mars) and treat it in the usual, selfish, utilitarian way. We have already screwed this planet up. Now they are considering going elsewhere. Of course, once we're there, we'll screw that up too. Here's an 'out-of-this-world' thought: Focus on population control and conservation to limit how badly we're screwing up the one and only world we're ever going to have."

EarlyOut-1524710:

"Planting a radio telescope on the far side of the moon, shielded from the radio noise generated by all of our technology, might well provide the kind of scientific bonanza that Hubble has created. "That's what's lacking in most the moon mission proposals: the promise of being able to carry out some real science. Most of the proponents of a lunar return offer little more than, 'It would be neat to go back and look around some more.' That's a little vague, given the cost and danger involved."

Pb in CA:

"Somebody explain to me why going to the surface of the moon is valuable. There is nothing there of any value.

OK, I've heard the idea of building a radio receiver on the far side. But, it would be more cost-effective to build a very-long-baseline radio receiver system using a fleet of satellites that stay in low-moon orbit, and half the time are shielded from earth radio noise. "If we are willing to accept the fact that robots are much better adapted to carrying out missions in space, then we can have a sustainable, affordable space exploration program. The Augustine Commission got it right in this regard. Personally, I have no problem in thinking of robots as extensions of humans, and saying 'we are exploring the surface of Mars' currently with Curiosity. "Here are the advantages of robots vs. humans on the moon:

- Robots can stay indefinitely - no return trip to Earth

- Energy supply is sun power - no need to take air, food and water

- Very close communication to humans back on Earth - 2.5-second round trip

- Cost of a mission is 1:2000 compared to sending humans "What is gained by sending humans?"

Cheezeweggie:

"I can't believe that we are trillions of dollars in debt and the government is seriously considering cutting health care for the elderly — but we can even consider borrowing money to go to the moon. Clean up the mess, then spend money on 'toys.' America can't afford this right now."

Stargazermom123:

"Yes, we're in bad shape here on Earth. In many ways. But we were born to look out and dream ... to explore. We went to the moon ... we have rovers on Mars, [including] one working years after it was supposed to die. Voyager 1 is reaching the end of our solar system, and will soon be beyond it — our first UFO. If we don't go back to the moon ... go to Mars ... [and] go beyond that someday, when we solve our petty differences here on Earth and put our minds to developing the mechanism to go outward into the unknown, what do we have to look forward to? What do young people have to dream about? When I stand outside on a clear night and look out at all the stars, I often wonder if anyone is looking back. Looking back and dreaming of places unknown and things never before seen, just as I am."

More about Apollo 17:

In addition to marking the 40th anniversary of Apollo 17's lunar departure, this Earthrise serves as today's offering for the Cosmic Log Space Advent Calendar, which features views of Earth from outer space on a daily basis from now until Christmas. Check out these other holiday goodies:

More space calendar entries: