Jupiter’s surface gravity is about 24.8 meters per second squared, roughly two and a half times the pull you feel standing on Earth. That number, though, comes with a significant asterisk: Jupiter has no surface. The value refers to a specific altitude in the atmosphere defined by a pressure threshold, and gravity varies across the planet because Jupiter is far from a perfect sphere. Thanks to the Juno spacecraft, scientists now have the most detailed gravity map of any planet besides Earth, and what it reveals about Jupiter’s winds, core, and influence on the rest of the solar system goes well beyond a single number.
What “Surface” Means on a Gas Giant
When planetary scientists quote a surface gravity for Jupiter, they are talking about the gravity at the 1-bar pressure level. One bar is roughly the atmospheric pressure at sea level on Earth, so it serves as a convenient reference point for a planet that is essentially a ball of gas and fluid with no ground to stand on. Everything below that altitude is denser atmosphere that gradually transitions into liquid and eventually into an exotic interior of compressed hydrogen.
At that 1-bar level, precise measurements put Jupiter’s equatorial radius at about 71,488 km and its polar radius at about 66,842 km, with a mean radius of roughly 69,886 km. These figures, refined using Juno data, are actually a few kilometers smaller than older estimates.
Why Gravity Is Not the Same Everywhere on Jupiter
Jupiter spins fast. A day lasts less than ten hours, which is remarkable for a planet more than eleven times wider than Earth. That rapid rotation flings material outward at the equator, giving the planet a noticeably squashed shape. The equatorial bulge means the equator is nearly 4,650 km farther from Jupiter’s center than the poles are.
This oblateness has direct consequences for gravity. At the poles, you are closer to the planet’s center of mass, so gravity is stronger. At the equator, you are farther away, and the centrifugal effect of the rotation works against gravity, making the effective pull weaker. The difference is substantial enough that surface gravity at Jupiter’s poles is meaningfully higher than at its equator.
Jupiter’s deep interior complicates things further. The planet does not rotate uniformly from top to bottom. Juno’s gravity measurements show that the deep interior rotates nearly as a rigid body, while the atmosphere above it has bands of jet streams moving at different speeds. The transition happens around 3,000 km below the cloud tops, where the electrical conductivity of the compressed hydrogen becomes high enough that magnetic forces suppress the differential rotation.1Nature. A suppression of differential rotation in Jupiter’s deep interior This layered rotation subtly reshapes the gravity field in ways that a simple spinning-sphere model would miss.
How Juno Mapped Jupiter’s Gravity
Before Juno arrived at Jupiter in 2016, our knowledge of the planet’s gravity field came from flybys by earlier spacecraft. Those encounters provided rough estimates of a few gravity harmonics, the mathematical terms that describe how the gravitational pull deviates from that of a perfect sphere. Juno changed the game by entering a polar orbit that repeatedly carried it close to Jupiter’s cloud tops, allowing its onboard gravity science experiment to track tiny changes in the spacecraft’s velocity with extraordinary precision.
The technique relies on Doppler tracking. Ground stations on Earth send a radio signal to Juno, and Juno bounces it back. As Jupiter’s gravity tugs on the spacecraft, its speed changes by fractions of a millimeter per second, shifting the frequency of the returned signal. By analyzing those shifts over dozens of close passes, scientists extracted both the even and odd gravity harmonics with unprecedented accuracy.2The Planetary Science Journal. Juno Spacecraft Measurements of Jupiter’s Gravity Imply a Dilute Core
The even harmonics describe the planet’s symmetric shape, things like how much Jupiter bulges at the equator. The odd harmonics reveal asymmetry between the northern and southern hemispheres. Before Juno, the odd harmonics were essentially unknown. The spacecraft’s measurements showed a clear north-south asymmetry in Jupiter’s gravity, a signature of internal flows and atmospheric dynamics that are not mirror images across the equator.3Nature. Measurement of Jupiter’s asymmetric gravity field
Analysis of 22 gravity passes also turned up something unexpected: time-variable gravity signals that could not be explained by the planet’s static shape. One leading explanation is that Jupiter oscillates, with large-scale normal modes (essentially planetary-scale vibrations) periodically redistributing mass inside the planet and leaving a faint but detectable imprint on the gravity field.4Nature Communications. Juno spacecraft gravity measurements provide evidence for normal modes of Jupiter If confirmed, this would make Jupiter one of the few bodies beyond the Sun where internal oscillations have been detected through gravity alone.
What the Gravity Field Reveals About Jupiter’s Interior
For decades, the standard picture of Jupiter’s interior was a tidy three-layer model: a molecular hydrogen envelope, a metallic hydrogen layer deeper down, and a compact core of rock and ice at the center containing perhaps ten to fifteen Earth masses of heavy elements. Juno’s gravity data challenged that picture almost immediately.
The measured values of certain gravity harmonics were hard to reproduce with a small, dense core. Instead, models that fit the data better feature a “dilute core,” a large region where heavy elements are mixed into the surrounding hydrogen and helium rather than concentrated in a tight ball at the center. This fuzzy core may contain ten to a few tens of Earth masses of heavy material spread across a region extending to nearly half of Jupiter’s radius.5Nature. The formation of Jupiter’s diluted core by a giant impact One intriguing explanation for how such a structure came about is a giant impact early in Jupiter’s history, when a large rocky body slammed into the young planet and stirred its core outward.
Interior models built on hydrogen-helium equation-of-state simulations confirm that including a dilute core helps reconcile the calculated gravitational harmonics with what Juno actually measured. The presence of the dilute core tends to reduce the absolute values of the higher-order even harmonics, bringing models into closer agreement with observations.6Geophysical Research Letters. Comparing Jupiter interior structure models to Juno gravity measurements and the role of a dilute core This matters for the gravity question because the distribution of mass inside the planet determines exactly how the gravitational pull varies with location and depth. A concentrated core and a diffuse core of the same total mass produce measurably different gravity fields at the 1-bar level.
Jet Streams That Reach Thousands of Kilometers Deep
Jupiter’s famous banded appearance reflects powerful east-west jet streams in its atmosphere. Some of these winds blow at hundreds of kilometers per hour. A longstanding mystery was whether those jets were shallow, weather-layer phenomena or features rooted deep in the planet’s fluid interior. Juno’s gravity measurements provided the answer: the jets extend roughly 3,000 km beneath the cloud tops.7Nature. Jupiter’s atmospheric jet streams extend thousands of kilometres deep
The connection between winds and gravity is straightforward in principle, though fiendishly complex in practice. Winds that blow at different speeds at different latitudes redistribute mass. Faster-moving gas gets pushed outward slightly by centrifugal effects, while slower-moving gas settles inward. This creates density variations that show up as asymmetries in the gravity field, specifically in the odd harmonics. Because the northern and southern hemispheres have different jet stream patterns, the gravity field is not symmetric across the equator.8Journal of Geophysical Research: Planets. The Range of Jupiter’s Flow Structures That Fit the Juno Asymmetric Gravity Measurements
Below the roughly 3,000-km mark, the planet’s interior becomes electrically conductive enough that the magnetic field acts as a brake on differential rotation. The deep interior then rotates more or less as one solid body, even though it is not solid at all. This transition zone is where the atmospheric dynamics end and the bulk-rotation regime begins, and it is gravity data that drew the boundary.
What Jupiter’s Gravity Does to Its Moons
Jupiter’s gravitational influence extends far beyond its own atmosphere. The planet hosts at least 95 known moons, and its gravity drives some of the most dramatic geological activity in the solar system. The clearest example is Io, the innermost of the four large Galilean moons.
Io orbits Jupiter on a slightly elliptical path, which means its distance from the planet changes continuously. As Io moves closer and farther away, the gravitational pull it experiences shifts in both strength and direction. This tidal flexing heats Io’s interior, powering hundreds of active volcanoes and making it the most volcanically active body we know of.9Nature. Io’s tidal response precludes a shallow magma ocean The energy source is not radioactive decay or primordial heat, as on most rocky worlds. It is the periodic, spatially uneven projection of Jupiter’s gravitational field across the moon’s body, literally kneading Io’s interior like dough with every orbit.10The Astrophysical Journal Supplement Series. TIDAL HEATING IN A MAGMA OCEAN WITHIN JUPITER’S MOON Io
Europa, the next Galilean moon outward, experiences a gentler version of the same tidal heating. The energy is thought to maintain a liquid water ocean beneath Europa’s icy crust, one of the most compelling targets in the search for habitable environments beyond Earth. Ganymede and Callisto, farther from Jupiter, feel less tidal stress, but even they show signs that tidal processes have shaped their interiors and surfaces over billions of years.
The orbital relationships among these moons are themselves a product of Jupiter’s gravity. Io, Europa, and Ganymede are locked in a 1:2:4 orbital resonance, meaning for every orbit Ganymede completes, Europa completes two and Io completes four. This resonance is maintained by gravitational interactions and is what keeps Io’s orbit slightly elliptical, perpetuating the tidal heating that would otherwise have circularized the orbit long ago.
Jupiter’s Gravitational Influence on the Solar System
Jupiter’s gravity shapes far more than its own moon system. With roughly 318 times Earth’s mass, it is the dominant gravitational player after the Sun, and its pull has sculpted the architecture of the entire solar system over billions of years.
The asteroid belt between Mars and Jupiter is a clear example. Jupiter’s gravity, particularly through orbital resonances, prevents material in that region from coalescing into a planet. Simulations show that when Jupiter and Saturn were in a near-2:1 orbital resonance early in the solar system’s history, chaotic excitation dynamically depleted and stirred the asteroid belt, leaving only a tiny fraction of the original population in stable orbits between roughly 2 and 3.25 astronomical units from the Sun.11PubMed Central. Terrestrial planet and asteroid belt formation by Jupiter–Saturn chaotic excitation Jupiter’s gravitational influence also organized asteroid families into specific resonant orbits, capturing and maintaining groups of asteroids at its Lagrange points and along other resonance paths.12Acta Astronautica. Jupiter, the great celestial organizer: On the origin of orbits of some asteroid families in mean motion resonances with Jupiter
There is a popular idea that Jupiter acts as a cosmic shield, using its gravity to deflect comets and asteroids that might otherwise strike Earth. The reality is more nuanced. Jupiter does capture or deflect some incoming objects, as it famously did with Comet Shoemaker-Levy 9 in 1994. But its gravity can also redirect objects inward toward the inner solar system. Whether Jupiter’s net effect on Earth’s impact rate is protective, neutral, or even slightly harmful remains debated among dynamicists.
Jupiter’s Faint Rings and Gravity’s Gentle Touch
Jupiter’s rings are nothing like Saturn’s spectacular ice bands. They are faint, dusty, and nearly invisible except in forward-scattered light. But they exist, and gravity is responsible for their structure. Observations from the Galileo spacecraft revealed that Jupiter’s outermost gossamer rings are actually two distinct rings, each bounded by the orbit of a small inner moon: Amalthea and Thebe. The rings’ unusual rectangular cross-sections and brighter edges are explained by dust knocked off these moons by micrometeorite impacts. The ejecta drifts inward under gravitational and electromagnetic forces, spreading into the thin sheets we observe.13PubMed. The formation of Jupiter’s faint rings
The rings illustrate a quieter side of Jupiter’s gravity. While the planet’s pull drives volcanic eruptions on Io and herds asteroids across the solar system, it also maintains delicate structures of microscopic dust grains in stable orbits. The balance between Jupiter’s gravitational pull, solar radiation pressure, and electromagnetic forces from the planet’s powerful magnetic field determines whether any given dust particle stays in orbit, spirals inward, or gets swept away entirely.
How Jupiter Compares to Other Giant Planets and “Hot Jupiters”
Jupiter’s surface gravity of about 2.5 g is high by solar system standards, but it is not the highest among the gas and ice giants. Saturn, despite being nearly as wide as Jupiter, has a much lower mass and a surface gravity only slightly above Earth’s. Uranus and Neptune, smaller and denser than Saturn but far less massive than Jupiter, fall somewhere in between. Jupiter’s combination of enormous mass and large radius gives it the strongest gravitational pull of any planet in our solar system, though the relationship between mass, radius, and gravity is not as straightforward as people sometimes assume. Doubling a planet’s mass does not double its surface gravity if the radius also increases.
Beyond our solar system, astronomers have discovered thousands of exoplanets in the general mass range of Jupiter, commonly called “hot Jupiters” when they orbit extremely close to their host stars. Many of these planets are surprisingly bloated, with radii well above Jupiter’s despite similar or lower masses, which means their surface gravities can be lower than Jupiter’s even though they are bathed in intense radiation. The most inflated examples tend to be highly irradiated and relatively low in mass; planets heavier than about five Jupiter masses generally do not have radii much above Jupiter’s own.14The Astrophysical Journal. THERMAL PROCESSES GOVERNING HOT-JUPITER RADII The physics behind this inflation is still an active area of research, with stellar heating, tidal interactions, and atmospheric dynamics all playing potential roles. Jupiter, sitting in the comparatively calm outer solar system, represents a useful baseline against which these exotic worlds are measured.
What It Would Feel Like
If you could somehow stand at Jupiter’s 1-bar level, which you cannot because there is nothing to stand on and the environment is lethal in numerous ways, you would weigh about two and a half times what you weigh on Earth. An 80-kilogram person would feel like they were carrying an extra 120 kilograms. Walking would be exhausting. Jumping would be disappointing. Your cardiovascular system, evolved for Earth’s gravity, would struggle to pump blood to your brain against the increased pull.
Spacecraft designers take this gravity seriously. Any probe sent into Jupiter’s atmosphere accelerates relentlessly as it descends, and the combination of speed and atmospheric density generates extreme heating and pressure. The Galileo atmospheric probe, which entered Jupiter in 1995, survived for about 58 minutes before the increasing pressure and temperature crushed and melted it at a depth corresponding to roughly 23 bars. The probe never came close to any solid material, because there likely is none until you reach the diffuse core region far below, where conditions are so extreme that hydrogen behaves like a liquid metal.
For future missions, Jupiter’s gravity also matters as a tool. Spacecraft routinely use Jupiter gravity assists to gain speed for journeys to the outer solar system or to shed speed for missions to the inner solar system. The planet’s massive gravitational well can change a spacecraft’s velocity by tens of kilometers per second in a single flyby, saving years of travel time and enormous amounts of fuel. Every mission to Saturn, Uranus, Neptune, or beyond Pluto has relied on, or could benefit from, a gravitational boost from Jupiter.