Mexico's Zone of Silence

by Brian Dunning
July 2, 2019

Deep in the interior of Mexico, in the Chihuahua desert, is a sparsely populated region of ranch land and vacant expanses. It's known for a curious trait: radios are said not to work there, and it's claimed that compasses only spin uselessly. But amid this eery radio silence — where commercial radio broadcasts are muted and even handheld walkie talkie sets are said to fail — are even more strange phenomena: weird lights in the sky, unusual UFOs, crazy meteor showers seen nowhere else on Earth, and even a creepy race of Nordic-looking aliens. This is the Zone of Silence, or Mapimí Silent Zone.

Geographically, it's on the western edge of the Bolsón de Mapimí, a hundred-thousand square kilometer sink into which rivers flow but none flow out of. Not being an officially recognized area, the Zone of Silence doesn't really have a specific size or location; most sources place it at about the point where the three states of Durango, Chihuahua, and Coahuila meet. But this vagueness of location has its purpose, as we'll soon see.

The Zone is said to overlap with the Mapimí Biosphere Reserve, a UNESCO site dedicated to studying the ecologically diverse flora and fauna, fed by the area's abundant water. The reserve includes a salt lagoon, a desert habitat, and a mountain habitat. Far from its popular reputation of an arid and desolate desert, the Mapimí region that includes both the reserve and the Zone teems with plants, animals, and some 76,000 people in towns and ranches. Exploring the Zone on foot would be a challenging prospect, as it's mostly privately owned ranch land, criss-crossed with barbed wire. Traipsing across these expanses can also be found another type of denizen: seekers of the strange, drawn from all over the world by the urban legends. Locals called them zoneros, literally "Zoners".

The 2018 movie Silencio was about the Zone (although it was ridiculously fictionalized). Gerry Hunt's 1986 book The Zone of Silence calls it "The Most Incredible Scientific Mystery Since the Bermuda Triangle" and lists the following phenomena:

GIANT UFOs
MYSTERIOUS EARTHEN PLATFORMS
GROTESQUE ANIMALS
FOOT-LONG INSECTS
RADIO COMMUNICATIONS LOST
NAVIGATIONAL EQUIPMENT GONE WILD
AND MUCH MORE!

The basic explanation for the Zone's radio silence offered up by its believers is that it has an affinity for iron-rich meteors. Something about the area, perhaps magnetism, draws them here; and as a result, the ground underfoot is thick with ancient and modern iron-rich meteorites. The belief is that the magnetic distortion from these meteorites is what jams radio signals and renders compasses useless. The association with ghost lights and UFOs and Nordic aliens is less clear, but they remain an important part of every article written about the Zone.

But the Zone's strangest detail is something that happened in 1970. The story goes that the United States launched a missile that accidentally landed in the Zone — no doubt drawn by the same forces that attract meteors. And not just any missile: it was said to be a dirty bomb, deliberately made to be extra radioactive. Aliens, magnetic anomalies, a radio dead area, and now a government conspiracy. The Zone of Silence has it all.

If you're a human being, as I am, you probably had the same first thought on this subject that I did, which was "Let's go down there for ourselves and see if our radios and compasses work." When there's a real mystery attached to a real place that's accessible, especially a reproducible mystery like radios being non-functional, it presents a tantalizing opportunity. Unsurprisingly, others have also had this thought, thus the multitudes of zoneros in the area. In addition, the local residents all have cell phones and radios as well. And, spoiler alert, it turns out that there is no problem with radios or compasses whatsoever. Researchers and rangers at the Biosphere Reserve use two-way radios with no trouble. That part of the Zone of Silence urban legend is pure fiction; and — not unexpectedly — it also happens to be the only part that was reproducible and would have been objectively testable. This raises a question: If it's so easy to discover that the Zone's basic manifestations are false, how then is the belief maintained?

Although most locals grudgingly tolerate the zoneros, some earn a few spare bucks guiding them around or demonstrating the uselessness of a compass. However, tricks with compasses are easy to perform — making a compass turn is one of the five tricks Uri Geller has made a career from. It takes only the smallest magnet, or even a lightly magnetized object, concealed in the hand, wristwatch, ring, anything. If a local has impressed any visitors by showing compasses moving on their own, judge for yourself whether it's more likely this common and easily performed trick was used, or whether there is indeed something unprecedented in nature making the magnetic field rotate dynamically in that precise location.

The basic claim is that the compass behavior is due to the meteors that fell in the region. This would not explain a moving compass, though. It is true that the whole world is covered with magnetic anomalies, caused almost entirely by geological structures which could include meteoric material. Have a look at any magnetic anomaly map of the Earth and you'll see that practically every point on the planet has some small variance from magnetic north. But these deviations are all tiny — far smaller that you could ever notice using a compass — and, importantly, they don't move. If you're shown a moving compass in the Zone of Silence, you're seeing a magic trick, not a geomagnetic anomaly. Express any doubt, and you'll be told that the Zone "moves around", a lucky consequence of not appearing on maps.

Local magnetic anomalies also would not produce a disruption in radio service, which is the usual claim of the zoneros. The electromagnetic field is an example of what we call a vector field. Every point in the universe is associated with a vector, which has both a direction and a magnitude. Think of tiny arrows at every point in space, each with a length and a direction, describing the electromagnetic field at that specific point. When you hold a magnet in your hand, you're altering the direction and magnitude of the vectors in your immediate vicinity. This universal vector field is not a disruption to radio signals; indeed, the opposite is true: it's what makes them possible. Radio waves passing through space cause these little vectors to oscillate. It makes no difference how strong they are or what direction they're pointing; it's their oscillation that carries the radio signal. So if the claim was true and powerful magnetic meteors are beneath the surface of the Zone of Silence, all that would mean to radio is that it's as good an environment as any to propagate radio signals.

We can also test the claim that there is an unusual number of magnetic iron meteors in the area. It's easy to do an online search of the Meteoritical Bulletin Database, and to plot the locations of all known significant meteorites on a digital map. There are only two near Mapimí: the Escalón, weighing 54 grams and discovered in 1979; and the Jaralito, weighing 11 kilograms and discovered in 1977. Hardly the massive magnetic sources claimed by the legends.

The meteorite mentioned most often in the literature about the Zone of Silence is the Allende, which fell in 1969 and weighs two tons. It was witnessed by many people in the United States and Mexico as a brilliant fireball streaking through the sky. However, it's nowhere near Mapimí, it's about 140 km to the west. It's also a type CV3 carbonaceous chondrite, the largest ever discovered, in fact; but it's not magnetic. It is, however, in a cluster. Within about 50 km of one another are six known meteorites, but all the others are tiny, less than a kilogram, except one: the Chupaderos, discovered in 1852 with fragments totaling 24.3 tons, and solid iron. This is a good size but it's not among the biggest known; and, as the sole large iron meteorite in the vicinity, and being located 130 km from Mapimí, it hardly supports the claim that many meteors are magnetically drawn into the Zone of Silence from space. This claim, too, turns out to be false.

But this conclusion doesn't apply to everything about the Zone. The story of the American rocket crashing down turns out to be true; in fact, it's one of the really wild stories to come out of the Cold War. An important detail is usually given wrong, which is that it was a missile carrying a "dirty bomb" warhead; but the rest is basically correct. The Athena RTV, which stood for Re-entry Test Vehicle, was a small rocket designed to put a test warhead into conditions that would simulate an actual missile re-entry. Its final two stages were actually fired upon descent to bring the warhead up to a simulated re-entry speed of about Mach 20. Over 140 such launches were conducted from 1964 to 1977, most launching from Green River, UT and impacting in White Sands, NM. Launch #V123D on July 11, 1970 carried an AS-5 Advanced Ballistic Re-entry System dummy warhead and developed a fault halfway through its flight. Rather than taking its planned high-speed dive into the ground, the vehicle was carried by its final two stages further south, into Mexico. Luckily, it impacted in the middle of nowhere; but unluckily, this particular re-entry vehicle contained cobalt-57, a dangerous radioactive compound. Its purpose was to measure how much of the ablative material covering the nosecone burned off during re-entry. But in the middle of Mexico, the only purpose it served was as a significant hazard to anyone who might come across it.

To make a long story short, the impact site was eventually located (given by one source as 26.7467º N, 103.7458º W) and the Mexican government and US Air Force cooperated in its cleanup. A temporary railroad spur was built to the site to facilitate collecting all the contaminated soil, which was then shipped north to White Sands for disposal.

What about author Gerry Hunt's other colorful wonders: the "mysterious earthen platforms, grotesque animals, and foot-long insects"? I found no reports of any such things outside of his book, and no mention of them from the people at the ecological preserve; so let's just chalk those up to one more imaginative author trying to sell a book.

So if you were planning to join the zoneros and take your compass and walkie-talkies down there for an adventure, you're probably better off bringing a riata and a cowboy hat instead, and lending a hand on one of the ranches. Just be careful with your whoops and shouts, because it is — after all — the Zone of Silence.

By Brian Dunning
Follow @BrianDunning