Mars is a rocky, desert world with terrain that dwarfs Earth’s most dramatic landscapes. The planet hosts the tallest volcano and the longest canyon in the solar system, along with vast plains, ancient river channels, and polar ice caps. Its surface splits into two strikingly different halves: smooth, low-elevation plains in the north and heavily cratered highlands in the south. From towering shield volcanoes to dried-up lake beds, the Martian landscape tells a story of fire, water, and billions of years of wind.
Two Halves of a Planet
The most fundamental feature of Mars is something you’d notice immediately from orbit. The planet is split roughly in half by what scientists call the crustal dichotomy. The northern hemisphere is younger, smoother, and sits at lower elevation. The southern hemisphere is older, higher, and pocked with impact craters. This division runs around nearly the entire planet and represents one of the biggest unsolved puzzles in planetary science. No one is entirely sure what caused it, though a massive ancient impact and internal geological processes are both candidates.
The elevation difference between these two halves is substantial. The southern highlands rise several kilometers above the reference point used as Mars’s version of sea level (called the areoid), while the northern lowlands sit well below it. The lowest spot on the entire planet is inside Hellas Planitia, a giant impact basin in the southern hemisphere that drops 8,200 meters below the areoid. That’s deeper below the Martian “sea level” than most of Earth’s ocean trenches are below ours.
Volcanoes Unlike Anything on Earth
Mars is home to Olympus Mons, the largest volcano in the solar system. Its peak reaches 21,229 meters above the Martian areoid, roughly two and a half times the height of Mount Everest. But height alone doesn’t capture how massive it is. Olympus Mons stretches about 700 kilometers across, making it over 20 times wider than it is tall. Its summit caldera alone is roughly 90 kilometers long by 60 kilometers wide. Standing at its base, you wouldn’t even realize you were on a volcano because the slope is so gradual it would disappear into the horizon.
Olympus Mons isn’t alone. Three more enormous shield volcanoes, known as the Tharsis Montes, form a line nearly 1,500 kilometers long in the Tharsis region. Each stands roughly 25 to 27 kilometers high, though they sit atop a broad lava plateau about 10 kilometers thick, so the volcanoes themselves rise about 15 kilometers from their immediate surroundings. These volcanoes grew so large partly because Mars has only 38% of Earth’s gravity, which allows rock and lava to pile higher before collapsing. The planet also lacks plate tectonics, so instead of a volcano drifting away from its magma source (as happens in Hawaii), the lava kept building in one place for hundreds of millions of years.
Valles Marineris: A Canyon Spanning a Continent
Stretching more than 3,000 kilometers across the Martian equator, Valles Marineris is long enough to reach from California to New York. It spans up to 600 kilometers wide in places and plunges as deep as 8 kilometers. For comparison, the Grand Canyon is 800 kilometers long, 30 kilometers across, and 1.8 kilometers deep. Valles Marineris could swallow the Grand Canyon many times over.
Unlike the Grand Canyon, which was carved primarily by river erosion, Valles Marineris likely formed through a combination of tectonic cracking of the crust and subsequent collapse. As the massive Tharsis volcanic region bulged upward billions of years ago, the surrounding crust stretched and fractured. Water may have played a role in widening parts of the canyon system later, and landslides have continued to reshape its walls. The result is a landscape of layered cliff faces, side canyons, and chaotic terrain that records billions of years of Martian geological history in its exposed rock.
Craters Everywhere
Impact craters cover much of Mars, especially the southern highlands. Without active plate tectonics or widespread water erosion to erase them, craters from billions of years of asteroid and comet impacts remain visible on the surface. Some are small pits just meters across. Others are enormous basins. Hellas Planitia, the deepest point on the planet, is an impact crater roughly 2,300 kilometers in diameter. Gale Crater, where NASA’s Curiosity rover operates, is 154 kilometers wide and contains a layered mountain at its center that was sculpted by wind over billions of years.
That mountain, called Mount Sharp, illustrates how craters on Mars become landscapes of their own. The crater was likely filled to the brim with sediment over time, and wind gradually removed an estimated 64,000 cubic kilometers of material, leaving the central mountain behind. Today, the wind continues shifting sand dunes and creating small ripples that move a few centimeters per day inside the crater.
The Red Dust and Soil
The Martian surface is covered in a layer of fine, loose material called regolith. Every landing site visited so far has found soil and dust with a basaltic composition, meaning it originated from volcanic rock. The signature rusty red color comes from nanoscale iron oxide particles scattered throughout the dust. About 15% of the iron in typical Martian soil exists in this oxidized form. These tiny particles are irregularly shaped with rounded edges, worn smooth by wind over enormous timescales.
The soil is also enriched in sulfur and chlorine compared to the underlying crustal rock, likely the result of chemical reactions between volcanic materials and the atmosphere over billions of years. Dust particles are extremely fine, less than 150 micrometers across (thinner than a human hair), and get lofted high into the atmosphere during dust storms. The dust is so pervasive and uniform across landing sites thousands of kilometers apart that it essentially represents a single global layer, constantly mixed and redistributed by wind.
Wind as the Dominant Sculptor
On Mars, wind is the primary force shaping the landscape today. The atmosphere is about a hundred times thinner than Earth’s, so Martian winds exert far less force. But time compensates for what air pressure lacks. Water hasn’t flowed on the surface in billions of years, there’s no active volcanism, and there are no tectonic plates recycling the crust. That leaves wind as essentially the only game in town, and over billions of years, even gentle sand-blasting adds up.
Orbiting spacecraft have documented long-term wind erosion patterns, shifting sand dunes, and dust devils spinning across the surface. The dust devils are whirlwinds that pick up loose material and leave dark streaks on the ground where they’ve cleared away the lighter surface dust. Larger features like yardangs (streamlined ridges carved by wind) dot the landscape in many regions. Sand dunes of various shapes, from crescent-shaped barchans to long ribbon-like linear dunes, are found across the planet and many are actively migrating today.
Ancient Rivers and Lakes
Some of the most striking terrain on Mars is evidence that water once flowed freely across the surface. The southern highlands are carved by valley networks, branching channel systems that look remarkably like river drainage patterns on Earth. These valleys sometimes filled craters with enough water to breach the crater rims, generating massive floods that carved outlet canyons stretching hundreds of kilometers.
Beyond erosional channels, Mars preserves actual sedimentary deposits from ancient rivers. In regions called Aeolis Dorsa and Arabia Terra, raised ridges trace the paths of former riverbeds. These ridges formed because river sediment hardened into rock that resisted erosion better than the surrounding material, so the old river channels now stand above the landscape rather than cutting into it. Fan-shaped landforms resembling river deltas sit at the edges of ancient lake basins. NASA’s Perseverance rover is currently exploring Jezero Crater, which contains one of these fossil deltas, collecting samples from what was once a lake bed. A recent study found that large drainage systems produced roughly half of all ancient river sediment on Mars, feeding major sedimentary basins at three key locations: Aeolis Dorsa, Arabia Terra, and Hypanis.
Polar Ice Caps
Both Martian poles are capped with ice that changes dramatically with the seasons. The permanent polar layered deposits are predominantly pure water ice, accumulated over long timescales as Mars’s orbit shifted. On top of this water ice, a seasonal layer of frozen carbon dioxide (dry ice) builds up each winter when temperatures drop low enough for atmospheric CO₂ to solidify and fall as snow or frost.
At the north pole, this seasonal layer of CO₂ snow and frost reaches a combined thickness of roughly 1.6 meters by late winter before sublimating back into the atmosphere during spring. The polar terrain includes dramatic layered cliffs, spiral troughs carved by wind, and fields of strange pits and mounds created as ice sublimates unevenly. These layers record Mars’s climate history in much the same way that ice cores on Earth preserve records of past atmospheres, making the poles one of the most scientifically valuable landscapes on the planet.