Fifty years ago, astronaut Bill Anders captured an iconic photo of Earth

(CNN) -- Fifty years ago, astronaut Bill Anders captured an iconic photo of Earth. Looking out a window of the Apollo 8 spacecraft on Christmas Eve, 1968, he glimpsed a splash of blue beyond the lunar surface. After a fumbling exchange in zero gravity, his crewmate Jim Lovell extended a roll of 70 mm color film. At 16:39 Universal Time , 240,000 miles from home, Anders aimed his Hasselblad camera and brought our world into focus in one of history's most famous photographs.

"Earthrise" transformed the first crewed mission to orbit the moon from a nationalistic bid for prestige in the Cold-War-era space race, into something more profound: a dawning appreciation of humanity's common destiny on a fragile planet in the vacuum of space.

The sight of Earth, bursting with color against the inky darkness of space and a barren moonscape, was "the most beautiful thing I'd ever seen," Anders told Andrew Chaikin, a writer who later recounted the photo's fascinating history for the Smithsonian. And the view was "totally unanticipated," Anders said, because the mission had been so focused on going to the moon.

Yet it was not their destination that captured the collective imagination, but the home they had left behind.

It was days before the astronauts returned home, and the film was developed and released by NASA to the public. Back on Earth, the reaction was euphoric. People across the globe were astonished at the image of a blue orb shrouded in wispy white clouds, its land surfaces betraying no national borders.

Commentators waxed lyrical, invoking the spiritual unity of humankind. Anders, Lovell and mission commander Frank Borman belonged to "a geographical unit we will be hearing about more in the future -- Earth," wrote the editors of the Houston Chronicle. The poet Archibald MacLeish offered his own elegy: "To see Earth as it truly is, small and blue and beautiful in that eternal silence as it floats, is to see ourselves as riders on the Earth together, brothers on that bright loveliness in that eternal cold."

For Americans, the miraculous photograph offered a moment of tranquility and transcendence after a year of turbulence that included the assassinations of Martin Luther King Jr. and Robert F. Kennedy. When President Lyndon B. Johnson left office in the weeks following the mission, he circulated the photo to world leaders (receiving a thank you note from North Vietnamese leader Ho Chi Minh, of all people ). Stewart Brand made it the cover of his counterculture bible, the "Whole Earth Catalog."

Of more enduring relevance, the serendipitous photo inspired the modern environmental movement. Legions of conservationists would later trace their awakening to Anders' space-age shot seen round the world, and the first Earth Day was launched in April 1970, a year and a half after the taking of the photo.

Earthrise also foreshadowed changes at NASA. It gradually evolved from a space-fixated organization, in which photos of the Earth were low-priority targets of opportunity, into a part-time environmental agency with its sights trained on Earth. President George H. W. Bush formalized this in 1989, launching NASA's Mission to Planet Earth. "Let us remember as we chase our dreams into the stars that our first responsibility is to our Earth, to our children, to ourselves," he explained. "Yes, let us dream, and let us pursue those dreams, but let us also preserve the fragile world we inhabit."

Unfortunately, our oasis has begun to fade. And the fault lies not in our stars, but in ourselves. Rather than being wise stewards of Earth, we have despoiled it to the brink of environmental catastrophe.

Consider the recent, harrowing report from the Intergovernmental Panel on Climate Change. Even if global temperature increases are limited to 2 degrees Celsius -- the Paris climate agreement threshold, which the world is nowhere close to achieving -- the impact will be calamitous.

Without a drastic course correction, we will face deadly heat waves, rampant wildfires, food insecurity, water shortages, violent storms, rising sea levels and disappearing coral reefs. The US government shares this bleak outlook (at least outside the White House and other climate-denying precincts). Last month, the National Oceanic and Atmospheric Administration warned Americans to prepare for devastating impacts on their economy, health and environment.

Meanwhile, ecologists have released jaw-dropping reports on the perilous state of nature. Populations of vertebrate species (mammals, birds, fish, reptiles, and amphibians) have plummeted by 60% on average since 1970. Insect species, too, are cratering worldwide. "Earth is losing biodiversity at a rate seen only during mass extinctions," concludes the World Wide Fund for Nature's ironically titled "Living Planet Report."

Looking back, the hope implicit in Earthrise seems misplaced. Yes, we have taken some steps to restore our planet, including its once-thinning ozone layer. But we have failed miserably on numerous other fronts, continuing to take the biosphere for granted. Instead of uniting to preserve our fragile planet, we have plundered the very life support system on which our survival depends.

That was the unmistakable message at the acrimonious global climate conference in Katowice, Poland, in December. With Earth hanging in the balance, the Trump administration redoubled its retrograde support for fossil fuels at the climate conference. Delegates finally agreed on a set of fundamental transparency measures, but only after an all-nighter in which they put off the most contentious issues until next year. Meanwhile, greenhouse gas emissions continue to accelerate "like a speeding freight train."

A mere half-century after Earthrise, we are racing toward Earthset.

The-CNN-Wire