The American flags planted by Apollo astronauts likely bleached pure white after 50 years of unfiltered solar radiation, leaving the most famous banners in history standing as a white canvas.

The six American flags planted on the Moon between July 1969 and December 1972 – starting with the nylon flag that Buzz Aldrin and Neil Armstrong piloted to the dust at Tranquility Base – are almost certainly no longer red, white and blue. After more than five decades of unfiltered UV radiation, strong solar winds, and temperature fluctuations from about 120 degrees Celsius in lunar day to extreme cold at night, the pigments have almost certainly broken down.

What remains is probably more eerie than the original photos suggest: five sets of upright flags casting shadows on the regolith, five rectangles of brittle nylon that may have faded toward a blank canvas.

NASA’s history of lunar flags indicates that the Apollo flag was a standard nylon pennant modified so that it appeared to be flying in an airless environment. the Lunar Science Society It was not a monument built for centuries. It was a practical device, hastily designed, intended to operate during a moonwalk and maintain its shape long enough for television cameras.

NASA and the Lunar Reconnaissance Orbiter Camera team have since confirmed that flags left at later Apollo sites appear to still be standing. The exception is Apollo 11. Buzz Aldrin said he saw the first flag struck by the lunar module’s ascent engine, and later orbital photographs agree with this account.

Standing, yes. Colorful, almost certainly not.

Flags were never built to last

Signs are not designed to be permanent monuments. They were nylon flags, modified with a hinged horizontal rod that made the fabric appear to fly in the airless lunar environment.

The team had weeks, not years, to solve the problem of planting a flag on a windless world. They chose nylon because it is light, packable, and available. No one asked them to make the dyes withstand half a century of cosmic exposure. The mission was to raise the flag in front of a television camera for the duration of the moonwalk.

That evening of broadcast was the real design brief.

What does sunlight do without an atmosphere?

On Earth, the atmosphere absorbs the most destructive part of the solar spectrum. The ozone layer blocks essentially all UVA, most UVB, and much of UVA. Even a flag that has been flown outdoors in Arizona for a decade is slowly fading in comparison to anything left exposed on the moon.

The moon has no such shield. Solar ultraviolet radiation reaches the moon’s surface without the same atmospheric filtering that protects materials on Earth. For dyed nylon, this is important. High-energy UV photons can break the chemical bonds that give synthetic dyes their color. Red pigments tend to be particularly at risk. Blue dyes may last longer, depending on their chemistry, but they are not immune.

The white areas of the flag were actually white. The red and blue areas were the colors most likely to disappear. After enough lunar days have passed, the flag stops looking like a flag and starts looking like an old rag.

The radiation environment is brutal in other ways, too

UV rays are just the beginning. The moon’s surface is also in the path of the solar wind — a continuous stream of protons and electrons traveling at hundreds of kilometers per second — and is periodically exposed to solar particle events that fling high-energy particles onto exposed material.

Radioactive decay of materials in space It is a serious engineering problem even for devices designed to survive. Solar cells are designed specifically for this environment, but protons, electrons and high-energy heavy ions can still create defects and reduce performance over the life of the mission. A consumer grade nylon flag does not have a similar defense.

Recent work by scientists at the University of New South Wales on Effects of electron irradiation on PERC and TOPCon solar cells It shows how charged particles can damage even solid silicon devices intended for space energy. Flags are not silicone devices. They are organic polymer textiles, woven from long carbon chains. Under ultraviolet light, ionizing radiation, and thermal cycling, these chains can break. The fabric becomes brittle. Topics weaken. Stitching gives way.

Then there is the temperature

Each lunar day lasts about 14 Earth days, followed by about 14 Earth days of darkness. Surface temperatures can fluctuate from about 120 degrees Celsius in direct sunlight to well below freezing in darkness or shade. The science at Tranquility Base, Hadley Rille, or Taurus-Littrow has seen hundreds of such cycles.

The glass transition temperature of nylon is about 50°C. Above it the polymer becomes more flexible. In extreme cold, it becomes more glassy and more fragile. Cycling between these states hundreds of times – while simultaneously being degraded by UV and particle rays – produces the equivalent of fatigue in the fabric. Microscopic fractures spread through the tissue. The threads that were once tight loosen, then break.

What orbital images actually show

The Lunar Reconnaissance Orbiter repeatedly photographed the Apollo landing sites from lunar orbit. The narrow-angle camera can resolve many surface features, including landing stages, rover tracks, and turbulent regolith around landing sites. The flags themselves are small, but their shadows can still be revealed.

In 2012, LROC team reported That American flags were still standing and casting shadows at all Apollo sites except Apollo 11. At the first landing site, no shadow similar to the standing flag appeared, which is consistent with Aldrin’s account that the flag was inflated during liftoff.

What pictures can’t tell anyone is the color of the fabric. There is no spectroscopic data accurate enough to distinguish pale red tape from bare nylon. The conclusion that the flags were bleached is an inference from materials science, not a direct observation. But the inference is strong. The harsh ultraviolet sunlight has almost certainly bleached the colors long ago.

Flags planted by each crew

Apollo 11, Tranquility Base, July 1969 – Believed to have crashed during liftoff. Apollo 12, Ocean of Storms, November 1969. Apollo 14, Fra Mauro, February 1971. Apollo 15, Hadley Reel, August 1971. Apollo 16, Descartes Highlands, April 1972. Apollo 17, Taurus Litro, December 1972.

The Apollo 17 science was exposed to lunar surface conditions for approximately 53 years. Previous flags contained more than 56.

Other things at landing sites change, too

Flags aren’t the only artifacts the environment is slowly rewriting. Aluminum descent stages, lunar rovers, scientific instruments, paintings mounted on stairs, and Descartes’ Charlie Duke family portrait are all subject to the same broad forces: ultraviolet radiation, charged particles, thermal cycling, abrasive dust, and micrometeor impacts.

Recent reports on The harsh surface environment of the Moon Focus on why future settlements will have to deal with coarse regolith, vacuum, intense radiation, and extreme temperature fluctuations. These same terms actually work on Apollo sites. Painted surfaces fade. The plastic is yellow and cracking. Adhesives outgas and fail. Even shoe impacts, sharp and obvious in the 1969 photos, are slowly softened by the quiet gardening of micrometeorite impacts.

So what remains after fifty-six years?

Five columns remain upright. Five horizontal bars remain extended. Five rectangles of what was once dyed nylon, now almost certainly the color of ancient bone. The stitches that held the lines together have likely come apart. Edges are likely to fray. In some places, the fabric may tear completely, leaving rough white streaks that do not flap at all, because there is no air to flap in them.

Flags were planted as a gesture. Armstrong and Aldrin remained on the surface for approximately two and a half hours. Planting the flag took minutes. No one on the ground in Houston was thinking about 2026, or 2069, or what ultraviolet light does to synthetic dyes over geologic time.

However, the flags, in their bleached state, may be a truer memorial than the colored bunting ever were. A flag whose color remained for half a century in a vacuum would be a lie about the shape of the moon. The flag gone white tells the truth: This is a place that erases things. Slowly, patiently, photon by photon, the moon recovers the fabric.

The next humans to stand at Tranquility Base – when they arrive – will not find the flag planted by Armstrong and Aldrin still standing. It likely fell in 1969. But at the other five sites, they may find white rectangles on curved columns, casting the same shadows the orbiter has been casting for years, the color long gone, and the gesture somehow still remains.