You’ve seen it everywhere. It sits on bathroom doors, adorns ancient statues, and pops up in every astrology app on your phone. Most people just call it the "male" sign. But long before it was a shorthand for gender, it was—and still is—the symbol for Mars.
It’s a circle with an arrow pointing out from the top right. Simple. Iconic. But why? Honestly, the story behind this little glyph is a mess of Greek mythology, medieval alchemy, and a bit of a linguistic "telephone game" that spanned two thousand years. If you think it's just a shield and a spear, you’re only halfway right.
What is the symbol for Mars actually supposed to be?
The most common answer you’ll get from a history buff is that the symbol represents the shield and spear of the Roman god of war. It makes sense. Mars was the guy you called when you wanted to conquer a neighbor. But if we dig into the paleography—the study of old handwriting—the roots are actually a bit more "nerdy" than "warrior."
Historians like William T. Stearn have noted that the symbol likely evolved from a Greek contraction. In ancient Greek, the planet Mars was called Thouros. It started with the letter Theta ($\theta$). Over centuries of scribes rushing through manuscripts, that handwritten Greek letter started to morph. The crossbar of the Theta drifted upward, eventually poking out of the circle to become the arrow we recognize today.
It’s basically the ancient version of a typo becoming a feature.
By the time the Renaissance rolled around, the "shield and spear" interpretation had fully taken over because it was easier to explain to people than Greek linguistic evolution. It’s a better story. Everyone understands a weapon; not everyone understands shorthand Greek.
Alchemy and the "Red" Connection
In the Middle Ages, you couldn't separate astronomy from chemistry. They were the same thing. Every planet was tied to a specific metal. Mars, being the red planet, was naturally linked to iron.
If you were an alchemist in the 14th century trying to turn lead into gold (good luck with that), you’d use the symbol for Mars to represent iron in your notes. Iron rusts. It turns red. Blood is full of iron and it’s red. Mars looks red in the night sky. The logic was circular and airtight for the time.
Johannes Kepler and other early astronomers used these symbols not just as decorative flair, but as a technical language. They needed a way to map the heavens without writing out "The Planet Named After the Roman God of War" every single time they did a calculation. This symbol was their shorthand.
It’s not just for planets anymore
Fast forward to 1751. Carl Linnaeus, the Swedish botanist who basically decided how we name every living thing, was writing Species Plantarum. He needed a way to distinguish between male and female plants without wasting precious page space. He borrowed the alchemical symbols.
- He used the Mars symbol for male plants.
- He used the Venus symbol (the circle with a cross) for female plants.
It stuck. It stuck so well that it eventually jumped from botany to zoology and finally to human sociology. It’s wild to think that a symbol used by a Greek scribe to save time 2,000 years ago is now the universal sign for a "Men's Room" at a highway gas station.
The Astronomer's Perspective
If you talk to an astronomer today, they still use the symbol for Mars, but mostly in a historical or shorthand context. You’ll find it in old-school star charts or specific celestial coordinates.
Modern NASA scientists don't really use it in their day-to-day coding—they’re more likely to use "MARS" or a numerical code—but the cultural weight of the symbol remains. It represents the "Red Planet" in a way no other icon could. It carries the weight of the Martian dust, the massive volcanoes like Olympus Mons, and the idea of human colonization.
Why the arrow points "Up and Right"
There is no "up" in space. So why does the arrow point that way?
In most historical documents, the arrow points toward the upper right. This wasn't a law, but it became a convention. Some psychologists and historians argue it represents "outgoing" energy or "assertion." In the context of the God of War, pointing a spear forward and upward is a gesture of attack or progress.
If the arrow pointed down, it would look like a heavy weight. If it pointed left, it might look like a retreat. The "top-right" orientation feels active. It feels like a planet that is moving.
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Common Misconceptions
People get this wrong all the time. Here are a few things that aren't true:
- It’s a stylized 'M': Nope. It has nothing to do with the Latin letter M.
- It was invented by the Romans: They didn't really use "symbols" for planets the way we do; that came much later in the Byzantine era.
- It's only about men: In science, it signifies the planet first, iron second, and biological sex third.
How to use this knowledge
If you're a designer, an enthusiast, or just someone who likes being the smartest person at the dinner table, understanding the symbol for Mars is about understanding the layers of human history. It's a bridge between the stars, the dirt (iron), and our own biology.
When you see that symbol now, don't just see a gender sign. See the Greek Theta. See the rusted iron of an alchemist's lab. See the spear of a god that ancient civilizations feared and respected.
To really get a feel for how these symbols shaped our view of the cosmos, you should look into the "Seven Metals of Antiquity." It explains how we linked the Sun to gold, the Moon to silver, and Mars to iron. Understanding that grid makes the entire history of Western science feel a lot more connected. You might also want to look up the symbols for the "newer" planets like Uranus and Neptune—they were designed much later and look completely different because they didn't have that ancient Greek "handwriting" baggage.
Basically, start looking at symbols as evolving languages, not just static pictures. They change because we change.