It was a tiring day on their journey.

The three men had left Florida only a few hours before, one day after the new moon, in the middle of the night.

Their responsibilities were distributed and there was hardly any time on board that was not meticulously planned with tasks.

The fact that a technically perfect snapshot was created was due to human curiosity and individual presence of mind.

And that this photo of Earth would become one of the most famous images of all time - even if previous Apollo missions had taken similar pictures - can be explained well in hindsight with the circumstances of the time.

But the controversies over what it actually shows and how to appropriately interpret it are as intense as ever decades later.

The Apollo 17 crew had just completed five hours of flight.

It was December 7, 1972. The Saturn V rocket had brought them into orbit, they had already orbited the earth twice.

Now, the third time, they came in front of the brightly lit earth.

She was forty-five thousand kilometers below them.

A rocket ignited, giving the capsule a final boost that would take it away from Earth for good.

There were thousands of things to do, scientific documentation was mandatory, and spontaneous photos were not actually planned at that moment.

Apollo 17 was to remain the last manned expedition to the moon for decades and remains so to this day.

The Mona Lisa of scientific photography

Suddenly one of the astronauts looked out the window.

It was exactly five hours and six minutes after takeoff.

There was the earth like no one had ever seen before.

He was amazed and acted immediately.

The man took the camera, a 70mm Hasselblad, and shot a series of four images in less than a minute.

He didn't say a word about it, either to the others or over the radio.

You can listen to and read about this silence and clicking.

Upon returning to Earth, the film was developed and the technician immediately recognized the superior quality of the razor-sharp and perfectly exposed photo number 2. You could see the fully lit, entire globe.

While it was winter in the northern hemisphere, the sun was high in southern Africa,

at the top was the Arabian Peninsula above the Horn of Africa, far to the south was white Antarctica far below Madagascar.

Bands of white clouds, red deserts and hints of green forests were less strong than the color of the atmosphere and oceans, framed by the blackness of space and perfectly circular, which gave the image its name: "Blue Marble".

The picture immediately appeared on the covers of newspapers and magazines.

It was picked up by advertising.

Each of us has seen it hundreds of times.

To date, it is NASA's best-selling photograph.

It has become an icon, the “Mona Lisa of scientific photography”, books have been written about it, generations of image scientists, philosophers and historians have interpreted it.

Some claim it is the most reproduced photograph of all time.

Others have referred to photography as the sum of all images, the "image of images".