Mars stands out from every other planet in the solar system in ways that go far beyond its famous red color. It hosts the tallest volcano and deepest canyon ever discovered, has an atmosphere where sound behaves unlike anywhere on Earth, and holds enormous reserves of water ice locked beneath its poles. Here’s what makes the fourth planet from the Sun genuinely one of a kind.
Why Mars Looks Red
The planet’s distinctive rust-orange color comes from iron minerals in the soil that have reacted with water and oxygen over billions of years, forming iron oxide, essentially the same chemical process as everyday rust on Earth. Wind has eroded this rusty material into fine dust and spread it across the entire planet, a process that continues today. Recent spacecraft observations suggest the specific shade of red is best matched by a type of iron oxide that contains water, called ferrihydrite, rather than simple dry rust.
The Largest Volcano in the Solar System
Olympus Mons rises 25 miles (40 kilometers) from base to summit, making it more than two and a half times the height of Mount Everest. Its base covers an area roughly the size of Arizona, yet its average slope is only about 5 percent. You could walk up its side without feeling much of an incline. The volcano grew so massive because Mars lacks the tectonic plate movement that shifts Earth’s crust. A volcanic hotspot simply kept building in one place for hundreds of millions of years.
A Canyon System Stretching Across a Continent
Valles Marineris is a system of canyons just south of the Martian equator that runs about 4,000 kilometers long. Placed on Earth, it would stretch from coast to coast across the United States. The individual troughs are typically 50 to 100 kilometers wide, merging into a depression as much as 600 kilometers across. In places, the canyon floor plunges 10 kilometers deep, six to seven times deeper than the Grand Canyon.
A Thin Atmosphere of Almost Pure Carbon Dioxide
Mars’s atmosphere is 95.3 percent carbon dioxide by weight, nine times the total amount of CO₂ in Earth’s far more massive atmosphere. Despite all that carbon dioxide, the atmosphere is extremely thin. Surface pressure is less than 1 percent of what you feel at sea level on Earth. That thinness has dramatic consequences: liquid water cannot persist on the surface, temperatures swing wildly between day and night, and there is almost no protection from solar radiation.
Sound Travels Differently on Mars
NASA’s Perseverance rover carried a microphone to Mars and captured something no one had heard before: actual audio from another planet. The recordings revealed that sound on Mars is slower, quieter, and stranger than on Earth. Low-pitched sounds travel at about 537 mph compared to Earth’s 767 mph, while higher-pitched sounds move slightly faster at 559 mph. That difference means low and high notes from the same source arrive at your ears at slightly different times, an effect that doesn’t happen on Earth.
The thin, cold carbon dioxide atmosphere also smothers sound over short distances. On Earth, a sound can carry roughly 213 feet before dropping off. On Mars, it fades at just 26 feet, and high-pitched tones are lost completely at that distance. A conversation on Mars, even if you could breathe, would be nearly impossible beyond arm’s length.
Gravity You Can Feel the Difference In
If you weigh 100 pounds on Earth, you’d weigh only 38 pounds on Mars. That’s 62.5 percent less gravity than you’re used to. A Martian day, called a sol, lasts 24 hours and 37 minutes, close enough to an Earth day that human sleep cycles could theoretically adjust. That combination of familiar day length and dramatically reduced gravity makes Mars the most human-compatible planet in the solar system besides Earth, which is one reason it dominates conversations about future settlement.
Massive Ice Reserves at the Poles
Both Martian poles are capped with ice, but the composition is more complex than it first appeared. The south polar layered deposits are dominated by water ice, which makes up at least 80.5 percent of the deposit’s area and accounts for 60 to 80 percent of its total volume, roughly 1.0 to 1.3 million cubic kilometers. Frozen carbon dioxide (dry ice) and dust fill in the rest. These ice reserves represent one of the most significant resources for any future human presence on Mars, both as a potential water supply and as a source of oxygen.
A Planet Without a Magnetic Shield
Mars has no global magnetic field generated by its core, unlike Earth. Early in its history it likely did, but the planet’s interior cooled and the dynamo shut down. What remains are intensely magnetized patches of crust, remnants of that ancient field frozen into the rock. These localized magnetic anomalies are one to two orders of magnitude stronger than similar patches found on Earth, the Moon, or Mercury. Without a planet-wide magnetic field, the solar wind has been slowly stripping away the Martian atmosphere for billions of years, which helps explain why it’s so thin today.
Two Small, Doomed Moons
Mars has two tiny moons, Phobos and Deimos, both irregular and potato-shaped. They’re far smaller than Earth’s Moon and are likely captured asteroids or remnants of an ancient impact. Phobos, the larger of the two, is slowly spiraling inward, closing the gap to Mars by about six feet every hundred years. At that rate, in roughly 50 million years it will either crash into the planet or break apart into a ring, giving Mars a brief, Saturn-like accessory before the debris rains down.
Active Exploration and Sample Return
Mars is the most explored planet beyond Earth. NASA’s Perseverance rover has been collecting and sealing rock and soil samples since 2021, the first step of an ambitious plan to bring Martian material back to Earth. NASA and the European Space Agency are developing the Mars Sample Return mission, currently targeting a launch no earlier than 2027. If successful, it would mark the first time samples from another planet have been delivered to Earth-based laboratories, where scientists could analyze them with instruments far too large and sensitive to send to Mars.