One of the articles of faith of the Apollo Moon landing is that the items left on the lunar surface will last, if not for all time, at least for millions of years. We can see the tracks left by the astronauts of each of the Moon landings. The disturbed earth – more accurately, disturbed regolith – reveals their hops and steps around each landing site. We can see the solitary, silent walk of Neil Armstrong to West Crater, we see the gyrations of the Lunar Rover around Descartes in the “Apollo 16 Lunar Grand Prix”.

Have a look at this image of the Apollo 11 landing site, taken by the Lunar Reconnaissance Orbiter (LRO) probe. Normally, it orbits at an altitude of 50km but, in 2011, it dipped down to just 21km altitude for a month, to map the lunar surface in high resolution. We see the abandoned descent stage of the Lunar Module and three of its four landing pads (the one to the left is in shadow). We see the seismometer (labelled “PSEP” for “Passive Seismic Experiment Package”). We see the small Laser Ranging RetroReflector (LRRR) that was used to bounce laser beams off the Moon to measure its exact distance with incredible accuracy. We see the camera, with the earth disturbed all around it. And, most of all, we see the dark tracks made by the astronauts as they disturbed the surface dust: Armstrong’s lonely and unscripted walk to the crater edge and his small detour on returning.

Let’s compare with the equivalent Apollo 17 image. The Apollo 17 astronauts ranged much further from their Lunar module – call sign, Challenger – so the area covered by the image is much larger:

One of the first things that we notice is that many of the tracks are double. Of course, the Lunar Rover had wheels separated by 182cm (6 feet, in old NASA units), meaning that we resolve clearly the two sets of wheel tracks. There is so much detail in the images, with their resolution of 25cm, that we need to see a blow-up to appreciate some items more clearly. Here is one such amplification, although with the Sun rather high, so there is little shadow. The image sharpening causes some striping but, north of Challenger, we see a large area of disturbed ground and, within it, a dot and a short, straight shadow. What was long and straight? The Apollo 17 flag pole, of course!

Of course, it is easy to dismiss this tiny detail as simply a small flaw in the image. However, LRO took other images of the site in different illumination conditions. The reason for this is that a high Sun was good for detecting brighter and darker areas on the surface – generally we see the tracks of the astronauts much better with the Sun high in the sky – but surface detail is seen better with a low Sun and more shadow, hence it was important for LRO to obtain images in a variety of lighting conditions. We can see from the fact that there is shadow within the craters and a much larger shadow from the Descent Stage of the Lunar Module that the Sun was much lower in this image. There, north of Challenger, is the same patch of disturbed ground and, within it, the same shadow, except now, with the lower Sun, it is larger. The size of the patch of disturbed ground shows just how much time the astronauts spent around the base of the Lunar Module and around the flag.

Only at one other landing site do we see a similar short, straight shadow. The Apollo 12 landing site is extraordinary for the pin-point landing made by Pete Conrad, right at the edge of the crater that holds the Surveyor 3, unmanned lander. We can see the tracks of the astronauts around the rim of the crater, walking towards the probe, before making the short descent down the crater wall.

Unlike Apollo 11, which made just one, short moonwalk, staying close to the Lunar Module, the Apollo 12 astronauts made two moonwalks, ranging much further from  it. We see the tracks going right around Surveyor crater, past Bench Crater, to Sharp Crater and then returning, north, past Head Crater. At this scale, only barely can we see a familiar feature north of Intrepid. Let’s look at a blow-up of the area around the Lunar Module.

There is that short, dark shadow again that shows that the flagpole is still standing proud.

These LRO images came as a surprise to NASA. It was known that the Apollo 11 flag had fallen: the astronauts had planted it too close to the Lunar Module and Buzz Aldrin could see it through his window, being blown over as the astronauts departed the surface. It was believed, until the LRO images, that the Apollo 12 flag had suffered a similar fate.

However, LRO images show no evidence of the Apollo 14, 15, or 16 flags. Given the difficulty that the astronauts had to hammer them into the soil, it is not so surprising that most were blown over on launch: they had served their ceremonial purpose and their survival was not important.

Alert readers will have noticed that, when I referred to images, I used the word “flagpole”, not “flag”. This was deliberate. Actually, it is extremely unlikely that any Apollo flag survives. There is a great deal of mystique about the flags and not a few conspiracy theories. However, the truth is, as in many cases, quite prosaic. We think of the flags as some high-tech marvels suitable for the greatest adventure in human history.

Ahem! Not quite true.

Actually, they were standard nylon flags of the kind that can be bought at any fairground. They were made by a New York company and each cost NASA the princely sum of $6.95. Yes! Six dollars and ninety-five cents. This is documented by NASA.

In fact, there are also dark rumours that the flag was very much an afterthought on Apollo 11, being added to the payload at the last moment. To make the flag “fly”, it was reinforced by wires and hung from a horizontal arm with a locking pin. Unfortunately, the pin failed in Apollo 12 and the flag drooped sadly.

The six flags that were planted had no special UV protection and have had to support a temperature range from about -170⁰C at night, to +130⁰C during the day, as well as a generous dose of extreme ultraviolet light from the Sun. The NASA verdict is that the colour was bleached out of the flags by the Sun many years ago, while a secondary effect of the solar ultraviolet has been to disintegrate the nylon. Most likely, not a thread of the flags survives. At best, there may be a few decaying, white fibres still flying.

So, even at the Apollo 12 and 17 landing sites, what we see is the straight shadow of the flagpole but, of the flag itself, which should certainly have been resolved at the Apollo 17 landing site, there is, as NASA predicted, no sign.

When, as is inevitable, a future automatic, or maybe even manned landing reaches one of the Apollo landing sites, as Apollo 12 itself visited the Surveyor 3 landing site, we will find the footprints of the astronauts, we will find the Lunar Modules, battered by the lift-off of the Ascent Stage, we will find the instruments and Lunar Rovers and, at some sites, even the exhausted backpacks that the astronauts threw out of the door to save space. All these will be unchanged. But we will find only bare flagpoles, without their flags.