With a day just 37 minutes longer than Earth's and a surface gravity only a third as strong, the dry, red world of Mars is a surprisingly familiar, yet profoundly alien, neighbor sculpted by numbers that tell a story of cold deserts, thin air, and ancient mysteries.
Key Takeaways
- Mars has an equatorial radius of 3,396.2 km and a polar radius of 3,376.2 km, giving it an oblateness of 0.0059
- The mean density of Mars is 3.9335 ± 0.004 g/cm³, which is about 71% that of Earth
- Mars has a surface gravity of 3.72076 m/s², approximately 38% of Earth's gravity
- Mars has a semi-major axis of 1.52366231 AU (227,939,100 km) in its orbit around the Sun
- The orbital eccentricity of Mars is 0.0934, causing significant variation in distance from Sun
- Mars' orbital period (sidereal) is 686.971 days (1.88085 Earth years)
- Mars' atmosphere is 95.32% carbon dioxide by volume
- Atmospheric pressure at Mars' surface averages 6.36 mb (0.63% of Earth's)
- Nitrogen makes up 2.59% of Mars' atmosphere
- Tharsis Montes volcanic region hosts Olympus Mons at 22.5 km height
- Valles Marineris canyon system stretches 4,000 km long, up to 7 km deep
- Hellas Planitia impact basin is 2,300 km wide, 7.1 km deep
- Mariner 4 flyby in 1965 returned 21 images covering 1% of surface
- Viking 1 lander operated 2,245 sols, analyzed 15 soil samples
- Pathfinder Sojourner rover traveled 100 m, lasted 83 sols
Mars is smaller, colder, and less dense than Earth with a thin atmosphere.
Atmosphere and Climate
- Mars' atmosphere is 95.32% carbon dioxide by volume
- Atmospheric pressure at Mars' surface averages 6.36 mb (0.63% of Earth's)
- Nitrogen makes up 2.59% of Mars' atmosphere
- Argon constitutes 1.93% of the atmosphere
- Oxygen is 0.174% by volume in Mars' atmosphere
- Water vapor ranges from 0.03% to 0.03% (variable)
- Carbon monoxide is 0.0747%
- Scale height of Mars' atmosphere is 11.1 km
- Atmospheric temperature at 0 km altitude averages 210 K (-63°C)
- At 100 km, temperature is 148 K
- Blackbody temperature is 209.8 K
- Bond albedo is 0.25
- Atmospheric thermal escape is significant, with Jeans parameter λ = 28 at exobase
- Dust opacity during storms reaches tau=5.0
- Polar CO2 ice cap volume in summer is 1.2 × 10^6 km³
- Residual north polar cap thickness is 1,000 km diameter, 300 m thick
- South polar cap can grow to 3,200 km diameter in winter
- Atmospheric circulation has three cells due to Coriolis effect
- Global dust storms recur every 1.5 to 3 Mars years (2.1-4.2 Earth years)
- Wind speeds on Mars can reach 30 m/s (110 km/h) in dust devils
- Helium abundance is 1.2 ppm
- Krypton is 30 ppb, xenon 4 ppb
- Methane plumes detected up to 0.7% of atmosphere locally
- Ozone column density peaks at 3.8 nm-equivalent
- Water ice clouds form at 40-50 km altitude
Atmosphere and Climate Interpretation
Mars has essentially built itself a thin, carbon-dioxide-filled terrarium so leaky and desolate that your average breath would be an act of industrial production, your skin would boil without a pressure suit, and a stiff breeze could summon a planet-wide dust storm that lasts for months.
Geology and Surface Features
- Tharsis Montes volcanic region hosts Olympus Mons at 22.5 km height
- Valles Marineris canyon system stretches 4,000 km long, up to 7 km deep
- Hellas Planitia impact basin is 2,300 km wide, 7.1 km deep
- Northern lowlands cover 40% of surface, average depth 5.5 km below datum
- Southern highlands have crater density >200 craters >16 km diameter per 10^6 km²
- Tharsis bulge spans 5,000 km, elevation up to 10 km
- Over 635,000 impact craters identified >1 km diameter
- Lava flows on Elysium Planitia cover 200,000 km²
- Gale Crater rim height is 4-5 km above floor
- Jezero Crater delta spans 20 km wide
- Recurring slope lineae (RSL) observed on 100+ sites, up to 500 m long
- Hematite spherules ("blueberries") 0.2-0.8 mm diameter in Meridiani Planum
- Clay minerals cover 4.6% of surface, concentrated in Noachian crust
- Phobos Deimos craters: Stickney on Phobos is 9.5 km diameter
- Polar layered deposits thickness up to 3 km in south pole
- Mangala Valles outflow channel 800 km long
- Syrtis Major Planum dark albedo region 1,500 km across
- Arabia Terra plateau has 5 km relief
- Acidalia Planitia smooth plains unit covers 5 million km²
- InSight detected 174 marsquakes, largest magnitude 4.7
- Cerberus Fossae fractures total 1,300 km length
Geology and Surface Features Interpretation
Mars is a planet of record-breaking extremes, from the solar system's tallest volcano and grandest canyon to ancient, battered highlands and vast, smooth plains, all whispering a complex geologic history of fire, ice, and relentless cosmic bombardment.
Human Exploration and Missions
- Mariner 4 flyby in 1965 returned 21 images covering 1% of surface
- Viking 1 lander operated 2,245 sols, analyzed 15 soil samples
- Pathfinder Sojourner rover traveled 100 m, lasted 83 sols
- Spirit rover drove 7.73 km over 2,208 sols before 2010 entrapment
- Opportunity rover odometry 45.16 km in 5,352 sols until 2018 dust storm
- Curiosity rover has driven 29 km as of 2023, drilled 39 rock samples
- Perseverance rover collected 24 rock samples by 2023, flew Ingenuity 72 times
- InSight lander measured 1,332 marsquakes over 1,000+ sols until 2022
- Mars Reconnaissance Orbiter imaged 99.9% of surface at 6 m/pixel CTX resolution
- Odyssey orbiter mapped global radiation levels, detected 640,000 craters >1 km
- Mars Express detected subsurface ice radar, mapped aurora
- MAVEN measured atmospheric loss rate of 100 g/s
- Tianwen-1 orbited, landed Zhurong rover 90 m drive in 2021
- Hope orbiter measured 2,500+ clouds in first year
- Mariner 9 mapped 85% of surface at 1 km resolution
- Phoenix lander confirmed water ice at 70 cm depth, operated 147 sols
- MOM (Mangalyaan) orbited 7.5 years, self-located relay failure in 2022
- Insight mole penetrated 2-3 cm into soil after 500+ cycles
- Ingenuity helicopter flew 72 times, total 128 min flight time by 2024
- Global Surveyor altimetry measured 1 m height accuracy over 40 million km²
- MRO HiRISE imaged 45,000+ targets at 25 cm/pixel
Human Exploration and Missions Interpretation
From humble flyby snapshots to sophisticated geological field trips and sky-scraping helicopters, our relentless campaign of robotic emissaries has collectively transformed Mars from a distant, blurry myth into a meticulously measured world of quakes, craters, ice, and ancient secrets waiting in a tube.
Orbital and Rotational Properties
- Mars has a semi-major axis of 1.52366231 AU (227,939,100 km) in its orbit around the Sun
- The orbital eccentricity of Mars is 0.0934, causing significant variation in distance from Sun
- Mars' orbital period (sidereal) is 686.971 days (1.88085 Earth years)
- Perihelion distance for Mars is 206,620,000 km (1.381 AU)
- Aphelion distance is 249,200,000 km (1.666 AU)
- Mars' orbital inclination to the ecliptic is 1.85061 degrees
- The longitude of ascending node for Mars is 49.558 degrees
- Argument of perihelion is 286.502 degrees
- Mean tropical year for Mars is 668.59 sols (686.98 Earth days)
- Mars' rotational velocity at equator is 240.6 m/s
- The solar day (sol) on Mars lasts 24.6597 hours
- Mars' synodic period with Earth is 779.94 Earth days
- Maximum angular size of Mars from Earth is 25.1 arcseconds
- Minimum angular size is 3.5 arcseconds
- Mars' opposition magnitude is -2.91
- Angular velocity in orbit is 0.524 degrees/day
- Mars' Hill sphere radius is 1,077,000 km
- The planet's orbital velocity at mean distance is 24.13 km/s
- Maximum orbital velocity is 26.50 km/s at perihelion
- Minimum orbital velocity is 21.97 km/s at aphelion
- Mars' precession rate of perihelion is 0.558° per Martian century
- The axial precession period for Mars is about 170,000 years
- Mars' mean motion is 0.191 Earth days per degree
- The planet experiences dust storms that can cover the globe every 3 Martian years on average
Orbital and Rotational Properties Interpretation
Mars, for all its fiery reputation, is a shockingly indecisive neighbor, taking nearly two of our years to complete its wildly eccentric, lopsided loop around the Sun, which makes its climate just barely hellish one season and then plunge it into a deep freeze the next, all while spinning at a near-identical pace to Earth and occasionally burying itself alive in global dust storms just to keep things interesting.
Physical Characteristics
- Mars has an equatorial radius of 3,396.2 km and a polar radius of 3,376.2 km, giving it an oblateness of 0.0059
- The mean density of Mars is 3.9335 ± 0.004 g/cm³, which is about 71% that of Earth
- Mars has a surface gravity of 3.72076 m/s², approximately 38% of Earth's gravity
- The escape velocity from Mars' surface is 5.03 km/s
- Mars' sidereal rotation period is 24.6229 hours (1.025957 sol)
- Mars completes one rotation on its axis every 24 hours, 37 minutes, and 22 seconds
- The axial tilt of Mars is 25.19 degrees, similar to Earth's 23.44 degrees
- Mars' mass is 6.4171 × 10^23 kg, which is 0.107 Earth masses
- The moment of inertia factor for Mars is 0.366, indicating a less centralized mass distribution than Earth
- Mars' surface area is 144,798,500 km², about 28% of Earth's
- Mars' equatorial surface gravity is 3.71 m/s²
- The planet's oblateness is calculated as (equatorial radius - polar radius)/equatorial radius = 0.0059
- Mars' volume is 1.6318 × 10^11 km³
- The core radius of Mars is estimated at 1,700–1,850 km based on InSight seismic data
- Mars' mantle thickness is approximately 1,500–1,800 km
- The crust thickness on Mars varies from 30–50 km in the southern highlands to about 10 km in the northern lowlands
- Mars' mean surface temperature is -60°C (-80°F)
- Diurnal temperature variation on Mars can reach 100°C due to thin atmosphere
- Mars' albedo is 0.25, reflecting 25% of incoming sunlight
- The planet's bulk density suggests a core composition of iron and sulfur at about 15-20% of total mass
- Mars' polar moment of inertia is 0.364
- The equatorial bulge of Mars is minimal at 20 km
- Mars' GM (standard gravitational parameter) is 4.282837 × 10^13 m³ s⁻²
- The planet's surface regolith density is about 1.5-2.0 g/cm³
- Mars' crustal density averages 2.9 g/cm³
- The internal heat flow on Mars is estimated at 20-22 mW/m²
- Mars' magnetic moment is less than 1.5 × 10^13 A m² today, remnant from ancient dynamo
- The planet's J2 gravitational harmonic is 1965.62 × 10^-6
- Mars C20 is -8.65 × 10^-6, indicating slight pear shape
Physical Characteristics Interpretation
Mars is so modestly squashed, so gently dense, and spins with such polite lethargy that it seems less a failed Earth and more a planet practicing mindful minimalism.
Sources & References
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- Reference 17HIRISEhirise.lpl.arizona.eduVisit source