Overview of Mars

The Red Planet

Mars is the fourth planet from the Sun, orbiting at an average distance of about 228 million kilometers (142 million miles). Named after the Roman god of war, Mars has fascinated humanity for thousands of years. Today, it stands as the most promising destination for human exploration beyond Earth.

From our night sky, Mars appears as a bright reddish point of light. That distinctive color comes from iron oxide — rust — covering much of its surface. But Mars is far more than just a rusty rock. It is a world with towering volcanoes, vast canyon systems, polar ice caps, and ancient riverbeds that hint at a warmer, wetter past.

Mars by the Numbers

Mars is roughly half the diameter of Earth, measuring about 6,791 kilometers (4,220 miles) across. Despite its smaller size, Mars has nearly the same amount of dry land area as Earth because it has no oceans. Its gravity is about 38% of Earth’s, meaning a person who weighs 100 pounds on Earth would weigh only 38 pounds on Mars.

A Martian day, called a sol, lasts 24 hours and 37 minutes — remarkably close to an Earth day. However, a Martian year is nearly twice as long as ours, lasting about 687 Earth days. This is because Mars orbits farther from the Sun and travels a longer path.

Two Small Moons

Mars has two small, irregularly shaped moons: Phobos and Deimos. Named after the Greek gods of fear and panic, these moons are much smaller than Earth’s Moon. Phobos, the larger of the two, is only about 22 kilometers (14 miles) across. Scientists believe both moons may be captured asteroids, though their exact origins are still debated.

Phobos orbits so close to Mars that it rises in the west and sets in the east, completing an orbit in just 7 hours and 39 minutes. Over millions of years, Phobos is slowly spiraling inward and will eventually either crash into Mars or break apart to form a ring.

A World of Extremes

Mars is a land of dramatic contrasts. It hosts Olympus Mons, the tallest known volcano in the solar system, rising about 22 kilometers (nearly 14 miles) above the surrounding plains — roughly two and a half times the height of Mount Everest. The planet also features Valles Marineris, a canyon system stretching over 4,000 kilometers (2,500 miles) long, making it roughly the width of the continental United States.

Temperatures on Mars are much colder than on Earth. The average surface temperature is about minus 62 degrees Celsius (minus 80 degrees Fahrenheit), though it can range from a relatively mild 20 degrees Celsius (68 degrees Fahrenheit) near the equator in summer to a frigid minus 140 degrees Celsius (minus 220 degrees Fahrenheit) at the poles in winter.

Why Mars Matters

Mars is the most Earth-like planet in our solar system. It has seasons, weather patterns, polar ice caps, and a 24-hour day cycle. Evidence strongly suggests that billions of years ago, Mars had a thicker atmosphere, warmer temperatures, and liquid water flowing across its surface. Understanding what happened to Mars — why it changed from a potentially habitable world to the cold desert we see today — helps scientists understand the processes that shape all rocky planets, including our own.

Mars is also humanity’s next great frontier. Multiple space agencies and private companies are developing the technology to send humans to Mars. When astronauts finally set foot on Mars, they will not only explore a new world but also take a giant step toward becoming a multiplanetary species — ensuring that humanity’s future extends far beyond Earth.

Exploring Mars

Since the 1960s, dozens of spacecraft have been sent to study Mars. Orbiters, landers, and rovers have mapped its surface, analyzed its rocks and soil, measured its atmosphere, and searched for signs of water and life. Notable missions include NASA’s Perseverance rover and Ingenuity helicopter, which arrived in 2021, and the ongoing work of the Curiosity rover, which has been exploring Gale Crater since 2012. Each mission brings us closer to answering fundamental questions about the Red Planet and preparing for the day when humans will walk on its surface.