Mars wasn’t “discovered” in a single moment the way Neptune or Pluto was. It’s one of the five planets visible to the naked eye, so humans have known about it for thousands of years. The real story of Mars is a series of discoveries, each one revealing something new about the red dot wandering across the night sky. From ancient stargazers who named it after a god of war to spacecraft that photographed its surface up close, our understanding of Mars built up over millennia.
Ancient Observers and the Red Wanderer
Mars is bright enough that no telescope is needed to spot it. Ancient civilizations across the world tracked its movement and gave it names tied to its distinctive reddish color. The Romans named it after their god of war because the color reminded them of blood. The Egyptians called it “Her Desher,” meaning “the red one.” Babylonian astronomers recorded its position in the sky as early as the second millennium BCE, recognizing it as one of the “wandering stars” that shifted against the fixed background of constellations.
These early observations were remarkably detailed. Ancient astronomers noticed that Mars occasionally appears to reverse direction in the sky, a phenomenon called retrograde motion. This puzzling behavior would take centuries to explain and ultimately played a key role in overturning the idea that Earth sat at the center of the universe.
Kepler and the Shape of Mars’s Orbit
The first major scientific breakthrough involving Mars came from Johannes Kepler, who inherited decades of painstaking observations from the Danish astronomer Tycho Brahe. Tycho made the most accurate astronomical measurements of his era, all without a telescope, and his records of Mars’s position were especially precise. Kepler spent years trying to reconcile that data with circular orbits and kept failing. The numbers simply didn’t fit.
In 1609, Kepler published “Astronomia Nova,” which laid out a radical conclusion: Mars does not travel in a circle around the Sun. It moves in an ellipse, with the Sun offset at one focus point rather than sitting in the center. This became Kepler’s first law of planetary motion. He also realized that Mars speeds up when it’s closer to the Sun and slows down when it’s farther away, his second law. These discoveries reshaped astronomy permanently, and it was Mars’s orbit, more than any other planet’s, that made them possible.
First Looks Through a Telescope
Galileo Galilei turned his telescope toward Mars in 1610, making the first accurate telescopic observations of the planet. His instrument was too weak to reveal surface details, but the act of viewing Mars through magnifying optics marked the beginning of a new era of planetary study.
Nearly 50 years later, in 1659, Dutch astronomer Christiaan Huygens used a better telescope and became the first person to sketch a recognizable feature on another planet. He identified a large dark patch now known as Syrtis Major, a volcanic region roughly the size of India. By watching this feature rotate in and out of view, Huygens was able to estimate how long a Martian day lasts. His measurement was remarkably close to the modern value of about 24 hours and 37 minutes. The observation also convinced him that Mars was a world with a real surface, not just a point of light.
The Canal Controversy
In 1877, Italian astronomer Giovanni Schiaparelli published maps of Mars showing dark, straight streaks stretching across the surface. He called them “canali,” an Italian word that simply means channels. But when translated into English, the word became “canals,” implying artificial construction. The distinction mattered enormously.
Schiaparelli’s canals appeared to connect dark areas that observers interpreted as oceans. Some scientists estimated the lines were dozens of miles wide and thousands of miles long. Speculation about intelligent Martian life exploded in both the scientific and popular press. The American astronomer Percival Lowell became the most enthusiastic champion of the idea, building an entire observatory in Arizona partly to study the canals and arguing that they were irrigation systems built by a dying civilization. Other astronomers struggled to see the canals at all and suspected they were optical illusions. Eventually, spacecraft imagery in the 1960s settled the debate: the canals don’t exist. They were artifacts of the human eye straining to find patterns at the limit of telescopic resolution.
Discovery of Mars’s Moons
The same year Schiaparelli mapped his canals, American astronomer Asaph Hall was searching for Martian moons using the 26-inch refractor at the U.S. Naval Observatory in Washington, D.C. After nights of fruitless scanning, he was ready to quit. His wife, Angelina, urged him to keep looking. The next night he spotted a tiny object near Mars, which turned out to be Deimos. Six nights later he found a second moon, Phobos. Both are small, irregularly shaped bodies, likely captured asteroids, and they remain the only known moons of Mars.
Identifying the Atmosphere
For centuries, astronomers could only guess what surrounded Mars. Early telescopic observers noted seasonal changes in the planet’s bright polar caps and shifting dark markings, hinting at some kind of atmosphere. But confirming what that atmosphere contained required spectroscopy, the technique of splitting light into its component wavelengths to identify chemical signatures.
In 1948, astronomer Gerard Kuiper at the University of Chicago used infrared spectroscopy to detect carbon dioxide in Mars’s atmosphere. This was a pivotal finding. It told scientists that the Martian air was fundamentally different from Earth’s and far too thin to support liquid water on the surface. It also set expectations for the harsh environment that spacecraft would later confirm.
The Space Age Reveals the Real Mars
On July 14, 1965, NASA’s Mariner 4 spacecraft made its closest approach to Mars and captured the first photographs of another planet taken from space. The 22 grainy images it returned showed a barren, cratered landscape that looked more like the Moon than the lush, canal-crossed world many had imagined. There were no signs of vegetation, no oceans, and no canals. The pictures also confirmed that Mars’s atmosphere was extremely thin, with surface pressure less than 1% of Earth’s.
Mariner 4 far outlasted its planned eight-month mission and provided critical data about how to safely send future spacecraft to Mars. Later missions built on its success. Mariner 9 became the first spacecraft to orbit Mars in 1971, revealing enormous volcanoes and a canyon system stretching nearly the length of the continental United States. The Viking landers touched down in 1976 and tested the soil for signs of life. Rovers like Spirit, Opportunity, and Curiosity have since driven across the surface, analyzing rocks and confirming that liquid water once flowed there billions of years ago.
Each generation of exploration has replaced imagination with evidence. Mars went from a red dot that ancient people named after a war god, to a world with supposed alien-built canals, to a cold, dry planet with a thin carbon dioxide atmosphere, ancient riverbeds, and the tallest volcano in the solar system. The discovery of Mars never really ended. It just kept getting more detailed.