Mars Facts
Everything worth knowing about the Red Planet — organized into four deep-dive guides.
🏔️ Geology & Surface
Mars is a world of superlatives carved in rock. Though it is only about half the size of Earth, it holds the largest volcano and the deepest canyon system in the solar system — a landscape shaped by billions of years of volcanism, impacts, and a gravity too weak to tear its giant structures down. Understanding that terrain is the first step to living on it.
Mars is Half the Size of Earth
Mars has a diameter of 6,779 km — about 53% of Earth's. Its surface area equals the total land area of all Earth's continents combined, despite being a much smaller planet.
Surface Gravity is 38% of Earth's
Mars has a surface gravity of 3.72 m/s² — about 37.6% of Earth's 9.8 m/s². A 150-pound person would weigh roughly 57 pounds on Mars. This lower gravity affects everything from human physiology to how buildings must be constructed.
Olympus Mons is the Tallest Volcano in the Solar System
At approximately 22 km high and 600 km in diameter, Olympus Mons dwarfs Mount Everest by nearly three times. It is a shield volcano so wide that standing at its base, you cannot see the summit — it lies beyond the horizon.
Valles Marineris Would Span the United States
The Valles Marineris canyon system stretches about 4,000 km long — roughly the distance from New York to Los Angeles. In places it reaches 7 km deep and 200 km wide, dwarfing the Grand Canyon.
Hellas Planitia is the Deepest Basin on Mars
The Hellas Planitia impact basin is approximately 7.2 km deep and 2,300 km wide. At its floor, atmospheric pressure is roughly double the Martian average — making it a prime candidate for early human settlement.
🌫️ Atmosphere & Climate
The Martian sky is thin, cold, and lethal to unprotected humans — but it is not empty. What little atmosphere Mars retains drives planet-swallowing dust storms, wild temperature swings, and the slow chemistry that future colonists will mine for breathable air. Every one of these facts traces back to a single ancient catastrophe: the day Mars lost its magnetic field.
Mars Once Had a Global Magnetic Field
Remnant magnetic signatures in ancient rocks indicate Mars once had a global magnetic field similar to Earth's. It ceased about 4 billion years ago when the planet's core cooled, after which the solar wind gradually stripped away much of the atmosphere.
Atmosphere is 95% Carbon Dioxide
The Martian atmosphere is composed of approximately 95.3% carbon dioxide, 2.7% nitrogen, 1.6% argon, and trace amounts of oxygen and water vapor. This makes it unbreathable for humans without life support.
Temperatures Swing Wildly
Surface temperatures on Mars range from about -195°F (-125°C) at the poles in winter to about 70°F (20°C) near the equator on a summer afternoon. The thin atmosphere means these swings can occur within a single day.
Dust Storms Can Engulf the Entire Planet
Mars experiences regional and occasionally planet-wide dust storms that can persist for months. The 2018 global dust storm blanketed the entire planet and caused NASA's Opportunity rover to lose power permanently after 15 years of operation.
🛰️ Water, Orbit & Moons
In the ways that matter most for human survival, Mars is eerily Earth-like. Its day is nearly ours, it tilts into four seasons, and it hides the one resource no settlement can live without: water ice, locked at the poles and just beneath the surface. Overhead, two captured asteroids race across the sky on strange, doomed orbits.
Water Ice Exists at the Poles and Underground
Mars has confirmed water ice at both polar caps and in the shallow subsurface at mid-to-high latitudes, confirmed by the Mars Odyssey orbiter and the Phoenix lander's direct excavation. This is the most critical resource for any future human settlement.
A Martian Day is 24 Hours and 37 Minutes
A Martian solar day — called a sol — lasts 24 hours, 39 minutes, and 35 seconds. This is remarkably close to an Earth day, making Mars among the most practical of all planets for human biological adaptation.
Mars Has Seasons Like Earth
Because Mars has an axial tilt of 25.19° (very close to Earth's 23.44°), it experiences four distinct seasons. Mars's more elliptical orbit means the southern hemisphere has shorter, more intense summers.
A Mars Year is About Two Earth Years
Mars takes 686.97 Earth days to complete one orbit. Earth and Mars align for efficient travel only once every 26 months, making launch windows precious for mission planners.
Mars Has Two Tiny Moons
Phobos and Deimos are Mars's two small, irregularly shaped moons, likely captured asteroids. Phobos orbits so close to Mars that it completes an orbit in just 7 hours 39 minutes — faster than Mars rotates — and will eventually crash into the planet in roughly 50 million years.
🚀 Human Exploration Firsts
For most of history Mars was a point of light. In a single decade, robotic explorers turned it into a place with a track record — proving that machines can fly in its thin air and that its own atmosphere can be turned into oxygen. These firsts are the proof-of-concept for everything a crewed mission will need.
Ingenuity Made First Powered Flight on Another Planet
On April 19, 2021, NASA's Ingenuity helicopter hovered for 39 seconds on Mars — the first powered, controlled flight on another planet. It carried fabric from the Wright Brothers' original Flyer.
MOXIE Proved Oxygen Can Be Made on Mars
In April 2021, NASA's MOXIE aboard Perseverance produced 5.37 grams of oxygen from the Martian atmosphere — enough for roughly 10 minutes of breathing. It proved the technology that could supply both air and rocket propellant for future missions.