In principle you could drive up Olympus Mons; getting onto it is the hard part. It rises about 22 km above the Martian datum, two and a half times Everest's height above sea level, but most of the climb is a 300 km flank averaging about a 5% grade, roughly 3 degrees. The obstacle is the edge: a cliff kilometres high rings almost the whole base, broken where later lava spilled over it into ramps. Mars Rally Championship, a free browser rally game, has no stage there, but its rover runs on the same 3.72 m/s² gravity.
How tall is Olympus Mons, and how big is it?
Olympus Mons is about 22 km (nearly 14 miles) tall by ESA's Mars Express figure, measured from the Martian datum: the reference level that stands in for sea level on a planet with no seas. From the plains at its foot the rise is closer to 25 km. Published heights run from about 21 km, by Mars Global Surveyor's laser altimeter, to 27 km in Viking-era maps.
It is about 600 km across, roughly the size of Arizona: more than twenty times wider than it is tall.
NASA calls it the largest known volcano in the solar system, and as a mountain it is roughly tied for tallest with the central peak of Rheasilvia, an impact basin on the asteroid Vesta. It stands northwest of the three Tharsis volcanoes and grew this large because Mars has no moving plates to carry it off its magma source: it kept building in one place for hundreds of millions of years.
Braking and cornering at 38% gravity are worked through in what it would be like to drive a car on Mars; this post takes the same physics up the biggest climb on the planet.
Olympus Mons vs Everest vs Mauna Kea
Olympus Mons is about two and a half times as tall as Everest, and more than twice Mauna Kea's height from the Pacific floor.
| Olympus Mons (Mars) | Mount Everest (Earth) | Mauna Kea (Earth) | |
|---|---|---|---|
| Summit height | ≈22 km above the Mars datum | ≈8.85 km above sea level | ≈4.2 km above sea level |
| Rise from its base | ≈25 km above the plains at its foot | No clean figure; it rises from the Himalaya | ≈10.2 km above the Pacific floor |
| Surface gravity | 3.72 m/s² | 9.81 m/s² | 9.81 m/s² |
| Energy to lift 3,000 kg to the summit | ≈68 kWh, from the datum | ≈72 kWh, from sea level | ≈34 kWh, from sea level |
| Summit air pressure | ≈72 Pa, about 12% of the Mars average | ≈33 kPa, about a third of sea level | ≈60 kPa, about 60% of sea level |
Lifting 3,000 kg, the mass of the rover in Mars Rally Championship, from the datum to the summit takes about 68 kWh (mass × gravity × height), slightly less than lifting it from sea level up Everest. The volcano is 2.5 times taller, Mars gravity is 0.38 times as strong, and the two nearly cancel. In energy terms, the biggest volcano in the solar system is an Everest.
The pressure row runs the other way: at about 72 Pa, the summit keeps 0.07% of Earth's sea-level pressure, and the top of Everest has more than 400 times as much.
How high is the cliff around Olympus Mons?
Olympus Mons does not end in foothills but in a cliff, Olympus Rupes, that runs almost all the way round it. The Lunar and Planetary Institute puts it at 2 to 10 km high, and where NASA's Mars Reconnaissance Orbiter photographed the northern edge, the cliff is nearly 7 km tall. At its tallest, the cliff alone rivals Everest.
It is steep rather than sheer. Where the rock is bare, slope maps made from orbit measure roughly 20 to 35 degrees from the top of the cliff to its foot, and one small stretch of the eastern scarp about 50. NASA's Space Exploration Vehicle, a pressurized-rover prototype, was built for 40-degree slopes, so on paper most of the face is climbable. The ground is the problem: kilometres of slope on layered lava and softer dust or ash, a face most scientists think landslides carved.
So the drive plan starts as a map search, and the map has an answer. NASA's caption for its Viking mosaic of Olympus Mons notes that lava flows drape over the scarp in places. Where they do, on parts of the east and southwest margins, the same slope maps measure only 2 to 6 degrees: ramps, not walls. Avoid the north and west approaches, where the plains lie under the aureole: giant ridges and blocks from ancient flank collapses that ESA traces some 1,000 km from the summit.
How steep is Olympus Mons?
Above the cliff, hardly steep at all. NASA's caption for a Mars Global Surveyor traverse of the summit puts the slopes at only a few degrees and says a person "would not really climb Olympus Mons, but simply walk uphill toward its summit." Averaged over the flanks, the grade is about 5%, roughly 3 degrees: a mountain highway, 300 km long.
The average hides the steps. The flanks are steepest in the middle and flatten toward the base, and the long northwestern side is gentler than the southeastern, where the middle flanks break into curved terraces stacked like fish scales, thought to have formed as the volcano's weight bent the crust. Underfoot is lava, the youngest of it perhaps only a few million years old by crater counts from ESA's Mars Express; nothing fresh shows at the summit, only a mantle of fine dust and small craters.
How long would the drive take?
Call it 300 km from the cliff to the caldera, allowing for a route that winds.
A robotic rover would need years. Perseverance is rated at 4.2 cm/s, so 300 km nonstop takes nearly three months; at its record pace, 411.7 m in one sol in June 2025, it takes about 730 sols, more than a Martian year. Its odometer in late August 2026, just under 45 km after five and a half years, is 15% of the distance; how fast Mars rovers go explains why they crawl.
Climbing is slower still: in fourteen years Curiosity has climbed more than 1,000 m above its landing site, on Mount Sharp. Olympus Mons asks for about twenty times that.
A crew changes the arithmetic. The Space Exploration Vehicle drives at about 10 km/h and supports two astronauts for up to 14 days, so 300 km is 30 hours at the wheel. Range is the catch: the 30-day NASA Mars concept in what a crewed pressurized rover would look like budgets up to 194 km of driving away from its recharging point, a third of a round trip to the caldera.
A rally rover makes it an afternoon: a little over five hours at 16 m/s (58 km/h), the average behind every gold par in Mars Rally Championship, or 75 minutes at the game's 240 km/h speed clamp. Neither pace would survive 300 km of unsurveyed lava, and the battery would not last the climb.
Does Mars gravity make the climb easier?
Cheaper, not easier. In the textbook friction model the steepest slope a tire can hold does not depend on gravity, because the slope's pull and the tire's grip both scale with it. At the 0.70 Mars Rally Championship uses for dry regolith, that is about 35 degrees on any planet. Cohesion, which weak gravity cannot shrink, tips it toward Mars; slip and sinkage tip it back, and Mars regolith explained has the soil mechanics.
Gravity cuts the cost instead. On the average 3-degree grade the pull back down is 0.19 m/s² on Mars against 0.51 on Earth, and holding 240 km/h up it takes under 75 kW, less than a quarter of the rover's 312.5 kW.
Energy is the real limit. From the plains below the cliff the lift is about 25 km, or 78 kWh; add about 37 kWh of rolling resistance over 300 km, at the game's 0.15 m/s², and the bill is about 115 kWh before any losses, more than the rover's 90 kWh battery holds. On paper, a real rover built to these numbers runs flat on the upper flanks.
Coming down, a 3-degree slope takes 0.19 m/s² out of the 3.1 m/s² grip budget, stretching the 125 m stop from 100 km/h, worked out in braking distance on Mars vs Earth, to about 134 m. The grade barely out-pulls rolling resistance, so a coasting rover gains only about 0.05 m/s², a minute to pick up 10 km/h. The biggest volcano on Mars is almost too gentle to freewheel down.
What you would see from the summit
Not a mountain. Mars curves away about one degree every 59 km, so between the summit and the cliff the planet itself bends through about 5 degrees, more than the flank's average slope. Look outward and the ground drops out of sight about 3.4 km away for a standing adult, no farther than on open plains, with the base hundreds of kilometres beyond and some 25 km below.
Look inward instead: a caldera of six overlapping collapse pits, about 60 by 80 km across and about 3 km deep, its far wall a low line on the horizon.
Most of the atmosphere, and most of the dust, is below you. When Mariner 9 reached Mars in November 1971, a planet-wide dust storm hid almost all of the surface: apart from the south polar cap, the only features showing were four dark spots, the summits of Olympus Mons and the three great Tharsis volcanoes.
What Mars Rally Championship models, and what it leaves out
No stage in Mars Rally Championship is on Olympus Mons, and none reproduces a real Martian place. The terrain is sculpted to Martian morphologies on a far smaller scale: the whole map is an 8.16 km square, and Stage 1's timed line descends 65 m. Olympus Mons is about 340 times that.
The physics that decides a climb does carry over: 3.72 m/s² of gravity, about 3.1 m/s² of grip, 312.5 kW and a 90 kWh battery. Scale does not: no 22 km climb, no kilometres-high cliff, no air thinning with altitude. The closest the game comes to Olympus Mons is a rare paint in the garage called OLYMPUS NAVY.
Where to try this
- Free roam has no timer and no checkpoints: climb the longest slope you can find, then brake from 100 km/h on the way down.
- How 3.72 m/s² gravity changes rally driving covers the cornering side of the same physics.
- Mars Rally Championship is free in a browser tab, with no download and no account. It runs on a phone in landscape or a school Chromebook, and up to eight pilots can race the same stage live.