Did you know that sunsets on Mars are blue? It sounds backwards for a planet named for its rusty red color, but it comes down to how sunlight scatters through Mars’ thin, dusty atmosphere: fine dust particles scatter red light away and let blue light travel more efficiently near the Sun, the opposite of what happens on Earth. NASA’s rovers have photographed it directly. That’s just one surprising detail about Mars, here’s the rest of its CV, the first entry in a new series profiling every planet in our solar system.

Basic Profile

  • Name: Mars
  • Type: Terrestrial planet
  • Position: 4th from the Sun
  • Diameter: 6,779 km (about half of Earth’s)
  • Mass: 6.42 × 10²³ kg (0.11 Earths)
  • Surface gravity: 3.71 m/s² (0.38 Earths, so a 100 kg person would weigh about 38 kg there)
  • Moons: 2 – Phobos and Deimos
  • Rings: None
  • Atmosphere: Thin – 95% carbon dioxide, 2.7% nitrogen, 1.6% argon, 0.7% oxygen, plus trace gases
  • Surface temperature: Average –63°C, ranging from –125°C to 20°C

Vital Stats

  • Age: About 4.5 billion years, it formed around the same time as Earth
  • Day length (a “sol”): 24 hours, 39 minutes, 35 seconds, strikingly close to an Earth day
  • Year length: 687 Earth days, or 1.88 Earth years
  • Distance from the Sun: 227.9 million km (1.52 AU)
  • Orbital speed: 24.077 km/s

How Far Is Mars From Earth, Really?

There’s no single answer, because both planets are orbiting the Sun at different speeds on different-sized paths, so the distance between them is constantly changing. At its closest, Mars comes within about 54.6 million km of Earth. At its farthest, the two planets can be as much as 401 million km apart, over seven times the closest distance. This is also why Mars missions are launched in specific windows every 26 months or so, when the two planets line up favorably.

Surface Features Worth Knowing

  • Valles Marineris: A canyon system roughly 4,000 km long – long enough to stretch across the continental United States, dwarfing Earth’s Grand Canyon.
  • Olympus Mons: The tallest volcano in the solar system at about 22 km high, roughly two and a half times the height of Mount Everest.
  • Polar ice caps: Made of a mix of water ice and frozen carbon dioxide (dry ice), growing and shrinking with the Martian seasons.

Atmosphere & Weather

  • The atmosphere is very thin, about 1% the pressure of Earth’s at sea level.
  • Global dust storms can engulf the entire planet and last for weeks.
  • Wind speeds can reach up to 160 km/h.
  • Evidence in the rock record suggests Mars had liquid water on its surface billions of years ago, before it lost most of its atmosphere.

Mars vs. Earth, Side by Side

  • Diameter: Mars 6,779 km vs. Earth 12,742 km
  • Gravity: Mars 3.71 m/s² vs. Earth 9.81 m/s²
  • Day length: Mars 24h 39m vs. Earth 24h 00m
  • Year length: Mars 687 days vs. Earth 365 days
  • Average surface temperature: Mars –63°C vs. Earth 15°C
  • Atmosphere: Mars very thin (mostly CO₂) vs. Earth thick (78% nitrogen, 21% oxygen)

Career Highlights: Human Exploration

  • Viking 1 & 2 (1976): The first missions to successfully land on Mars.
  • Spirit & Opportunity (2004): Rovers that explored the Martian surface far beyond their planned mission length.
  • Curiosity (2012–present): Still active, studying whether Mars could ever have supported life.
  • Perseverance (2021–present): Searching for signs of ancient life and collecting samples for eventual return to Earth.
  • Ingenuity Helicopter (2021): The first powered, controlled flight on another planet.

Did You Know?

  • Mars is called the “Red Planet” because of iron oxide – literally rust – covering its surface.
  • A year on Mars is nearly twice as long as a year on Earth.
  • Mars holds two solar system records at once: the largest volcano and the largest canyon.
  • Scientists keep studying Mars for three big reasons: understanding its past climate, searching for signs of past life, and evaluating its potential for future human habitation.

That’s Mars’ CV. Next up in this series: another planet, another set of numbers worth actually remembering. If there’s a particular planet you want covered next, let us know.

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