Since Galileo Galilei’s groundbreaking observations of Jupiter in 1610, this colossal planet has captivated scientists and astronomers alike. Jupiter, the undisputed giant of our Solar System, continues to puzzle and intrigue us, even after centuries of study and numerous space missions. Its sheer size, immense mass, unique composition, enigmatic magnetic and gravitational fields, and a vast system of moons make it a world profoundly different from our own Earth. Comparing Jupiter and Earth highlights the incredible diversity of planets within our cosmic neighborhood and underscores just how special our home planet truly is.
Size, Mass, and Density: A Tale of Two Extremes
When we talk about planetary dimensions, the contrast between Jupiter and Earth is nothing short of staggering. Earth has an average radius of 6,371 kilometers (3,958.8 miles) and a mass of 5.97 × 1024 kg. Jupiter, on the other hand, dwarfs Earth with a mean radius of 69,911 ± 6 km (43,441 miles) and a mass of 1.8986 × 1027 kg. To put it simply, Jupiter is approximately 11 times wider than Earth and boasts a mass nearly 318 times greater.
However, despite its enormous size and mass, Jupiter is significantly less dense than Earth. Earth, a terrestrial planet composed of rock and metal, has a density of 5.514 g/cm3. Jupiter, a gas giant primarily made of hydrogen and helium, has a density of only 1.326 g/cm3. This lower density is a key characteristic of gas giants, distinguishing them from the rocky terrestrial planets like Earth.
Size comparison of Jupiter and Earth highlighting the vast difference in scale between the two planets. Credit: NASA/SDO/Goddard/Tdadamemd
This difference in density also impacts surface gravity. Earth’s surface gravity is what we experience as normal gravity, about 9.8 m/s² or 1 g. While Jupiter lacks a solid surface in the same way Earth does, if we consider the point in Jupiter’s atmosphere where the pressure is equal to Earth’s sea-level pressure (1 bar), the gravitational force is a much stronger 24.79 m/s², or about 2.528 g. This means you would weigh over two and a half times your Earth weight on Jupiter’s “surface”.
Composition and Structure: Rocky Core vs. Gaseous Giant
Earth and Jupiter also present fundamentally different compositions and internal structures. Earth is a terrestrial planet, built from layers of silicate minerals and metals. Its structure is differentiated into a metallic core, a silicate mantle, and a crust. The core itself is further divided into a solid inner core and a liquid outer core. As you descend into Earth, both temperature and pressure steadily increase. Earth’s shape is an oblate spheroid, slightly flattened at the poles and bulging at the equator due to its rotation.
Jupiter, in stark contrast, is a gas giant. It’s predominantly composed of hydrogen and helium in gaseous and liquid states. Its atmosphere, which makes up the outermost layer, is about 88–92% hydrogen and 8–12% helium by volume. By mass, it’s roughly 75% hydrogen and 24% helium, with the remaining percentage consisting of trace elements. These trace elements include methane, water vapor, ammonia, silicon compounds, benzene, and other hydrocarbons, along with traces of carbon, ethane, hydrogen sulfide, neon, oxygen, phosphine, and sulfur. Frozen ammonia crystals even form clouds in the upper atmosphere.
Diagram illustrating Jupiter’s internal structure and atmospheric composition, showcasing its layers of hydrogen and helium. Image Credit: Kelvinsong CC by S.A. 3.0
Beneath the atmosphere, Jupiter’s interior becomes denser, composed of roughly 71% hydrogen, 24% helium, and 5% other elements by mass. Scientists believe Jupiter has a core made of a dense mixture of elements, possibly rocky, surrounded by a layer of liquid metallic hydrogen mixed with helium and an outer layer primarily of molecular hydrogen. Like Earth, temperature and pressure increase dramatically as you go deeper into Jupiter. At the “surface” (1 bar pressure level), the temperature is around 340 K (67 °C, 152 °F). Deep within, where hydrogen transitions to a metallic state, temperatures are estimated to reach 10,000 K (9,700 °C; 17,500 °F) and pressures 200 GPa. At the core boundary, temperatures could reach a scorching 36,000 K (35,700 °C; 64,300 °F) and pressures 3,000–4,500 GPa. Like Earth, Jupiter is also an oblate spheroid, but with a greater polar flattening due to its rapid rotation.
Orbital Parameters: A Year on Earth, a Decade on Jupiter
Earth and Jupiter’s journeys around the Sun are vastly different, dictated by their orbital parameters. Earth’s orbit is nearly circular, with a minor eccentricity of about 0.0167. Its distance from the Sun varies from 147,095,000 km (0.983 AU) at its closest point (perihelion) to 151,930,000 km (1.015 AU) at its farthest (aphelion). The average distance, 149,598,261 km, is defined as one Astronomical Unit (AU).
Diagram showing the asteroid belt located between the orbits of Mars and Jupiter in the inner Solar System. Credit: Wikipedia Commons
Earth completes one orbit around the Sun in approximately 365.25 days, defining our year. Its axial rotation, a sidereal day, takes 23h 56m and 4s, but a solar day (sunrise to sunrise) is 24 hours. Earth orbits the Sun and rotates on its axis in a counterclockwise direction when viewed from the celestial north pole. The Earth’s axis is tilted 23.4° relative to its orbital plane, causing our seasons as different hemispheres receive varying amounts of sunlight throughout the year.
Jupiter, much further out in the Solar System, orbits the Sun at an average distance of 778,299,000 km (5.2 AU), ranging from 740,550,000 km (4.95 AU) to 816,040,000 km (5.455 AU). At this distance, a Jovian year, one orbit around the Sun, takes 11.86 Earth years, or 4,332.59 Earth days. While its year is long, Jupiter boasts the fastest rotation of any planet in our solar system, completing a rotation in just under 10 hours (9 hours, 55 minutes, and 30 seconds). Therefore, a Jovian year is about 10,475.8 Jovian solar days.
Atmospheres: From Gentle Breeze to Gigantic Storms
Earth’s atmosphere, essential for life, is structured into five main layers: the troposphere, stratosphere, mesosphere, thermosphere, and exosphere. Air pressure and density decrease with altitude. The troposphere, the lowest layer, holds about 80% of the atmosphere’s mass and is primarily composed of nitrogen (78%) and oxygen (21%), with trace amounts of water vapor, carbon dioxide, and other gases. The troposphere is where most of Earth’s weather occurs, including clouds, rain, and storms. The thermosphere is home to the auroras, the Northern and Southern Lights.
The banded atmosphere of Jupiter with the prominent Great Red Spot, a massive storm larger than Earth. Credit: NASA
Jupiter’s atmosphere, as mentioned, is primarily hydrogen and helium, with trace elements. Like Earth, Jupiter also has auroras near its poles, but they are far more intense and almost constant due to strong radiation, Jupiter’s powerful magnetic field, and material from volcanic moon Io. Jupiter is known for its extreme weather. Winds in zonal jets can reach 100 m/s (360 km/h) or even 620 kph (385 mph). Massive storms can form in hours, spanning thousands of kilometers. The Great Red Spot, a colossal storm raging for centuries, is a prime example, although it has been observed to be shrinking. Jupiter’s atmosphere is perpetually cloudy, with ammonia crystals and possibly ammonium hydrosulfide clouds arranged in bands at different latitudes. These cloud layers are about 50 km (31 mi) deep and may have underlying water clouds, evidenced by powerful lightning detected in Jupiter’s atmosphere.
Composite image showing Jupiter’s hyper-energetic X-ray auroras as observed by Chandra X-Ray Observatory and Hubble Space Telescope. Credit: NASA/CXC/UCL/W.Dunn et al/STScI
Moons: One Lonely Moon vs. a Lunar System
Earth has a single, prominent natural satellite, the Moon. Known since prehistory, it has influenced mythology, astronomy, and Earth’s tides. It’s been a focus of scientific study and the only celestial body humans have walked on. The prevailing theory suggests the Moon formed from debris of a collision between Earth and a Mars-sized object about 4.5 billion years ago. The Moon is tidally locked to Earth, always showing the same side.
Illustration of Jupiter and its four largest moons, the Galilean satellites: Io, Europa, Ganymede, and Callisto. Credit: NASA
Jupiter, in contrast, possesses a vast system of 95 currently confirmed moons. The four largest, the Galilean moons (Io, Europa, Ganymede, and Callisto), discovered by Galileo, are worlds in their own right. Io is volcanically hyperactive. Europa is thought to harbor a subsurface ocean. Ganymede is the largest moon in the Solar System. Callisto may also have a subsurface ocean and has an ancient surface. Beyond the Galilean moons, Jupiter has an Inner Group of small moons and numerous Irregular Satellites in distant, eccentric orbits, likely captured asteroids or fragments from collisions.
In almost every aspect, Earth and Jupiter are fundamentally different worlds. Jupiter, a gas giant of immense proportions, and Earth, a small, rocky planet teeming with life, offer a fascinating study in planetary diversity. Ongoing missions like NASA’s Juno continue to unveil the mysteries of Jupiter, further deepening our understanding of this giant planet and highlighting the unique characteristics of our own precious Earth.
