Mars has gravity, and it pulls at roughly 38 percent the strength of Earth’s. In concrete terms, if you weigh 150 pounds on Earth, you would weigh about 57 pounds on Mars. That difference comes down to Mars being a smaller, less massive planet, but “smaller” understates the gap: Mars has only about 11 percent of Earth’s mass packed into a body with roughly half Earth’s diameter. The result is a gravitational environment strong enough to hold an atmosphere and keep your boots on the ground, yet weak enough to change virtually everything about how objects fall, fluids flow, muscles work, and landscapes form.
Where the Number Comes From
Earth’s surface gravity is about 9.8 meters per second squared. Mars clocks in at about 3.7 meters per second squared. The ratio gives you that familiar “38 percent” figure. Gravity depends on two things: how much mass a body contains and how far you are from its center. Mars loses on both counts. Its mass is far smaller, and although its smaller radius partly compensates (putting you closer to the center), the mass deficit dominates. The result is a gravitational acceleration less than two-fifths of what you are used to.
This number is not a rough estimate. Decades of orbiter missions have refined Mars’s gravity field to extraordinary precision. The Mars Reconnaissance Orbiter, for instance, used X-band and Ka-band radio tracking to map tiny fluctuations in the spacecraft’s velocity as it circled the planet, which revealed the gravitational tug of every mountain, basin, and subsurface mass concentration below.1Journal of Geophysical Research: Planets. Mars Reconnaissance Orbiter Radio Science Gravity Investigation Current gravity-field models still rely on ground-based tracking of range and Doppler signals between Earth stations and Mars orbiters, a technique that has been continuously improved since the late 1990s.2The Astronomical Journal. Mars Gravity Field Determination Based on Satellite-to-Satellite Tracking Technique
Gravity Is Not Uniform Across Mars
Just as Earth’s gravity varies slightly from the Himalayas to the ocean floor, Mars’s gravity is uneven across its surface. The planet hosts the solar system’s tallest volcano, Olympus Mons, and one of its deepest canyon systems, Valles Marineris. Massive volcanic provinces pile extra rock in one region; giant impact basins remove it elsewhere. These variations create “gravity anomalies” that orbiting spacecraft can detect as tiny accelerations and decelerations. Recent modeling work attributes part of the large-scale gravity signal to the flexing of Mars’s outer shell under volcanic loads and to slow convective flow deep in the mantle, while shorter-wavelength residuals correlate with crustal density differences and surface geological structures.3Journal of Geophysical Research: Planets. Describing the Global Gravity Field of Mars With Lithospheric Flexure and Deep Mantle Flow
For everyday human purposes on the surface, these anomalies are tiny, fractions of a percent. You would not feel a difference walking from one side of Mars to the other. But for navigation, orbital mechanics, and understanding the planet’s interior, they matter enormously.
What Mars’s Interior Tells Us About Its Pull
A planet’s gravity is ultimately a reflection of what lies beneath its surface. Mars appears to have a metallic core, but one that is less dense and proportionally larger than you might expect if it were pure iron. Modeling based on Mars’s gravitational field coefficients and precession rate suggests the planet has a solid inner core roughly 840 kilometers across with a density near 6,950 kilograms per cubic meter, implying a significant fraction of lighter elements mixed in with the iron.4Acta Physica Sinica. Constraining the size and density composition of the Martian core by using second-order potential coefficient and recent precession rate of gravity field model By comparison, Earth’s inner core is denser and sits beneath a much thicker mantle. That overall lower density throughout Mars is a big part of why its surface gravity is so much weaker despite the planet being only about half as wide as Earth.
Walking, Running, and Skipping on Mars
One of the first things you would notice on Mars is how different it feels to move. On Earth, your legs work as inverted pendulums during a normal walk, swinging forward while gravity pulls you down at just the right rate to make the exchange of energy efficient. Reduce gravity to 0.38g and that exchange breaks down at the speeds you are used to. Research using pendular energy models found that on Mars the optimal walking speed drops to about 2.5 kilometers per hour, roughly half the comfortable pace on Earth, and the overall range of efficient walking speeds shrinks accordingly.5The Journal of Physiology. The Role of Gravity in Human Walking: Pendular Energy Exchange, External Work and Optimal Speed
Want to go faster? Predictive gait simulations suggest you would not simply break into a run the way you do on Earth. At moderate speeds on Mars, skipping turns out to be the most energy-efficient gait when the goal is to minimize fatigue, while running only wins when the model optimizes for raw effort per step.6PubMed Central. Predictive simulation of gait at low gravity reveals skipping as the preferred locomotion strategy Apollo astronauts famously adopted a bouncy, loping gait on the Moon at one-sixth gravity. Mars gravity sits between the Moon and Earth, so the biomechanical sweet spot likely lies somewhere between a lope and a jog, with a skip thrown in when you want to cover ground quickly without tiring out.
What Reduced Gravity Does to the Human Body
Living for months or years in lower gravity does not just change how you walk. It reshapes your physiology. Most of what we know about reduced-gravity biology comes from studying microgravity on the International Space Station, where astronauts experience near-zero gravity. Mars offers about a third of Earth’s pull, which raises a genuinely open question: is 0.38g enough to protect the body from the worst effects of weightlessness?
Muscles
A recent experiment aboard the ISS exposed mice to graded gravity levels using an onboard centrifuge. The results were encouraging but mixed. At 0.33g, close to Mars gravity, the cross-sectional area of the gravity-sensitive soleus muscle was preserved. However, the shift from slow-twitch to fast-twitch muscle fibers, a hallmark of spaceflight deconditioning, was only partially suppressed at that level. It took 0.67g to fully prevent that fiber-type transition and to maintain grip strength and overall muscle performance.7PubMed Central. 0.33g mitigates muscle atrophy while 0.67g preserves muscle function and myofiber type composition in mice during spaceflight In plain terms, Martian gravity may be enough to keep muscles from visibly shrinking, but not enough to keep them working at full capacity without additional exercise.
The Cardiovascular System
On Earth, your heart and blood vessels constantly work against gravity to push blood upward from your legs to your brain. Remove that challenge, and the cardiovascular system deconditions: the heart can shrink, blood volume drops, and standing up after a long stretch of weightlessness can cause fainting. Researchers have tried to map how the cardiovascular system responds at specific partial-gravity levels, including Mars-equivalent gravity at roughly 0.38g, using tilt-table models that simulate reduced gravitational load along the body’s long axis. The emerging picture is a continuous dose-response curve where cardiovascular stress increases gradually with gravity, and Mars sits in an intermediate zone, not as benign as microgravity for the heart but not demanding enough to fully replace Earth-level conditioning.8PubMed Central. Dose-dependent effects of graded altered gravity during hypovolaemia on central haemodynamics and cardiovascular autonomic regulation
Balance and Spatial Orientation
Your sense of balance depends heavily on the vestibular system in your inner ear, which uses gravity as a reference signal for “which way is up.” In reduced gravity, that reference weakens, and the brain has to recalibrate how it integrates signals from the eyes, inner ear, and limbs. Research on hypogravity environments indicates that Mars-level gravity alters the sensorimotor mechanisms underlying spatial orientation, perception, and manual task performance.9PubMed Central. Perceptual and sensorimotor adaptations to hypogravity: implications for manual task performance and verticality perception For astronauts arriving after months of weightlessness during the transit from Earth, the sudden reintroduction of even partial gravity could cause disorientation, clumsiness, and difficulty judging distances, a serious concern for people who need to perform precise tasks immediately after landing.
Countermeasures for the Transit and the Stay
The trip to Mars takes roughly six to nine months in near-zero gravity. Arriving in decent physical shape to function at 0.38g, and eventually returning to Earth’s full gravity, is one of the central medical challenges of crewed Mars missions. Artificial gravity produced by spinning a spacecraft or a section of it has long been proposed as a broad-spectrum countermeasure, simultaneously loading the musculoskeletal, cardiovascular, and vestibular systems the way natural gravity does.10PubMed Central. Artificial gravity as a countermeasure for mitigating physiological deconditioning during long-duration space missions
Whether short bouts of centrifugation are enough has been tested in bed-rest studies designed to mimic the effects of weightlessness on Earth. A 60-day study conducted jointly by NASA, the German Aerospace Center, and the European Space Agency compared 30 minutes of daily centrifuge exposure to six 5-minute sessions spread throughout the day, both at 1g at the body’s center of mass.11PubMed Central. Assessing the effects of artificial gravity in an analog of long-duration spaceflight: The protocol and implementation of the AGBRESA bed rest study The broader research consensus is that targeted exercise, fluid management, and possibly hypergravity interventions during transit can help preserve muscle mass, cardiovascular stability, and postural control.12PubMed. Gravity, microgravity, and artificial gravity: physiological effects, implementation, and applications The open question is whether any of these interventions can fully compensate for months of zero-gravity travel followed by indefinite residence at one-third gravity.
Growing Food Under Martian Gravity
If humans are going to stay on Mars, they need to eat, and that means growing plants in a gravitational environment those plants never evolved for. Plants use gravity to orient their roots downward and shoots upward through a hormone-transport system. Reduce gravity to Mars levels, and that system goes haywire. Experiments simulating Martian gravity found that seedlings activate stress-response hormone pathways and certain transcription factors associated with acclimation, suggesting that plants can sense the reduced pull and try to adjust.13PubMed Central. Red Light Enhances Plant Adaptation to Spaceflight and Mars g-Levels
Maize experiments add another layer of complexity. Under simulated Mars gravity, genes controlling the directional transport of the growth hormone auxin were significantly upregulated in roots, essentially cranking up the volume on the gravitational sensing system. But when Martian soil simulant was introduced, those same genes reversed course dramatically, with the gene most involved in root gravitropism showing the strongest suppression.14PubMed Central. Maize (Zea mays L.) survival on Mars depends on regolith’s chemical composition rather than reduced gravity or lack of magnetic field The takeaway is that gravity alone is not the biggest obstacle to Martian farming. The chemistry of the soil may matter more, and the two stressors interact in ways that lab experiments are only beginning to untangle.
How Reduced Gravity Reshapes the Landscape
Mars’s weaker gravity leaves fingerprints all over its geology. Mountains can grow taller because the crust can support more weight per unit area before collapsing, which is part of why Olympus Mons reaches roughly two and a half times the height of Everest. Canyons can cut deeper, cliffs stand steeper, and landslides travel farther before friction brings them to a stop.
Water behaves differently too. Experiments simulating water flowing over sediment under Martian gravity found that lower gravitational acceleration allows larger sediment pellets to be levitated by boiling water underneath them, and those pellets stay airborne longer, travel farther, and carve bigger channels than they would on Earth under the same temperature conditions.15PubMed Central. Water induced sediment levitation enhances downslope transport on Mars This helps explain some of the peculiar channel-like features on Martian slopes that do not quite match what we would expect from simple liquid erosion under Earth-like conditions.
Even dust behaves differently. Mars’s thin atmosphere combined with its lower gravity creates a planet-wide dust cycle in which roughly 400 teragrams of dust are lofted into the atmosphere every year, settling back down and depositing a layer about 50 to 100 micrometers thick across the surface.16Elsevier / Icarus. Quantitative analysis of the Martian atmospheric dust cycle: Transported mass, surface dust lifting and sedimentation rates That may sound trivial, but over months and years this dust coats solar panels, clogs mechanical joints, and poses a respiratory hazard for any future crew. Lower gravity means particles stay suspended longer and travel farther before settling, making dust management on Mars a persistent engineering headache.
Landing Spacecraft in Weak Gravity and Thin Air
Mars’s gravity is weak enough that you might expect landing to be easy. It is not. The problem is the atmosphere: Mars has one, but it is less than one percent as dense as Earth’s. On Earth, parachutes and aerodynamic drag do most of the work of slowing a vehicle. On Mars, a parachute helps, but the air is too thin to slow a heavy lander enough. Meanwhile, the gravity is too strong for a soft touchdown under parachute alone, unlike on a body with negligible gravity where you might drift to the surface. This awkward middle ground, too much gravity for free-fall, too little atmosphere for aerodynamic braking, makes the entry, descent, and landing phase one of the hardest challenges in Mars exploration.17Acceleron Aerospace Journal. Aerodynamic Study of Successful Mars Entry Vehicles Every successful Mars lander has needed a combination of heat shields, parachutes, and powered descent, or in the case of the Mars Exploration Rovers, airbags. The Curiosity and Perseverance rovers used a rocket-powered sky crane to hover and lower themselves on a tether, a solution that would be absurd on Earth but was necessary given the Martian gravity-atmosphere mismatch.
Mars, Phobos, and Tidal Gravity
Mars’s gravity does not just affect what is on its surface. It reaches out and grips its two tiny moons, Phobos and Deimos. Phobos orbits so close to Mars that it completes a lap in just under eight hours, faster than Mars rotates, which means it rises in the west and sets in the east from the Martian surface. That proximity creates a strong tidal interaction: Mars’s gravity is gradually pulling Phobos inward, and tracking Phobos’s orbital decay over time has given scientists a way to study Mars’s interior properties from the outside in. The secular acceleration of Phobos’s orbit corresponds to a tidal energy dissipation rate of about 3.34 megawatts, the highest fractional rate of change in orbital angular velocity measured for any natural satellite in the solar system.18Journal of Geophysical Research: Planets. Improved estimate of tidal dissipation within Mars from MOLA observations of the shadow of Phobos The rate at which this energy dissipates tells researchers about the viscosity and thermal state of Mars’s deep interior.19PubMed. The rheology and thermal history of Mars revealed by the orbital evolution of Phobos In a few tens of millions of years, Phobos will either crash into Mars or be torn apart by tidal forces into a temporary ring, a reminder that even a modest gravitational field, given enough time, can reshape an entire moon system.