Ever since Galileo Galilei turned his telescope towards the heavens in 1610 and observed Jupiter, humanity has been captivated by this giant of our Solar System. Jupiter isn’t just the largest planet we know in our cosmic neighborhood; it’s a world brimming with mysteries that continue to challenge scientists, even after centuries of observation and numerous space missions.
One of the key reasons Jupiter remains so enigmatic is its sheer difference from our home, Earth. From its colossal size and mass to its exotic composition, powerful magnetic and gravitational fields, and a complex system of moons, Jupiter showcases the incredible diversity possible among planets. Understanding these contrasts between Earth and Jupiter offers invaluable insights into planetary formation, evolution, and the potential for life beyond our world. Let’s delve into a detailed comparison to truly appreciate the unique characteristics of each.
Size, Mass, and Density: A Tale of Two Worlds
When it comes to physical dimensions, Earth and Jupiter are in completely different leagues. Earth, our terrestrial home, has a mean radius of 6,371 kilometers (3,958.8 miles) and a mass of 5.97 × 10^24 kilograms. In stark contrast, Jupiter, the gas giant, boasts a mean radius of 69,911 ± 6 kilometers (43,441 miles) and a staggering mass of 1.8986 × 10^27 kilograms.
To put it simply, Jupiter is nearly 11 times wider than Earth and possesses approximately 318 times more mass. Imagine fitting over 1,300 Earths inside Jupiter! Despite its enormous size and mass, Jupiter is significantly less dense than Earth. Earth, being a terrestrial planet composed of rock and metal, has a density of 5.514 grams per cubic centimeter, whereas Jupiter, primarily made of gas and liquid, has a density of only 1.326 grams per cubic centimeter. This is only slightly denser than water.
This difference in density profoundly impacts surface gravity. Earth’s surface gravity is what we experience daily, measured at 9.8 meters per second squared (9.8 m/s²) or 1 g. While Jupiter, as a gas giant, lacks a solid surface, scientists define its “surface” as the point in its atmosphere where the pressure equals Earth’s sea-level atmospheric pressure (1 bar). At this level, Jupiter’s gravitational force is a powerful 24.79 m/s², equivalent to 2.528 g. If you could stand on Jupiter’s cloud tops (hypothetically, of course!), you would feel more than twice as heavy as you do on Earth.
Size comparison of Jupiter and Earth, highlighting the immense difference in scale. Credit: NASA/SDO/Goddard/Tdadamemd
Composition and Structure: Rock vs. Gas
The fundamental building blocks of Earth and Jupiter are vastly different, leading to their contrasting structures. Earth is a terrestrial planet, built from layers of silicate minerals and metals. These materials are differentiated into a metallic core, surrounded by a silicate mantle and a crust. Earth’s core itself is further divided into a solid inner core and a liquid outer core, the latter generating Earth’s magnetic field through its motion. As you descend from Earth’s crust towards its core, both temperature and pressure steadily increase. Earth’s shape is an oblate spheroid – a sphere slightly flattened at the poles and bulging at the equator due to its rotation. This equatorial bulge makes Earth’s diameter at the equator about 43 kilometers (27 miles) larger than its pole-to-pole diameter.
Jupiter, on the other hand, is a gas giant, composed predominantly of hydrogen and helium in gaseous and liquid states. Its structure is characterized by a gaseous outer atmosphere enveloping a denser interior. Jupiter’s upper atmosphere is primarily composed of hydrogen (88-92%) and helium (8-12%) by volume, and approximately 75% hydrogen and 24% helium by mass, with trace amounts of other elements making up the remaining percentage. This atmosphere also contains minute quantities of methane, water vapor, ammonia, silicon-based compounds, benzene, and other hydrocarbons, along with traces of carbon, ethane, hydrogen sulfide, neon, oxygen, phosphine, and sulfur. In the outermost atmospheric layer, crystals of frozen ammonia have even been observed.
Diagram illustrating Jupiter’s internal structure and composition, showcasing its layers of hydrogen and helium. (Image Credit: Kelvinsong CC by S.A. 3.0)
Beneath the atmosphere, Jupiter’s denser interior is estimated to be about 71% hydrogen, 24% helium, and 5% other elements by mass. Scientists believe Jupiter possesses a core composed of a dense mixture of elements, possibly rocky, although this remains uncertain. Surrounding this core is a layer of liquid metallic hydrogen mixed with helium, and an outer layer predominantly composed of molecular hydrogen. Similar to Earth, temperature and pressure within Jupiter escalate dramatically as you move towards the core. At the “surface” (1 bar pressure level), the pressure is around 10 bars, and the temperature is about 340 Kelvin (67 °C, 152 °F). Deeper within, where hydrogen transitions to a metallic state, temperatures are estimated to reach 10,000 Kelvin (9,700 °C; 17,500 °F) and pressures around 200 Gigapascals (GPa). At the core boundary, temperatures could soar to 36,000 Kelvin (35,700 °C; 64,300 °F), with interior pressures possibly reaching 3,000–4,500 GPa.
Jupiter, like Earth, is also an oblate spheroid, but its polar flattening is significantly more pronounced – 0.06487 ± 0.00015 compared to Earth’s 0.00335. This greater flattening is a consequence of Jupiter’s rapid rotation, causing its equatorial radius to be approximately 4,600 kilometers larger than its polar radius.
Orbital Parameters: Paths Around the Sun
Earth and Jupiter follow distinct paths in their orbits around the Sun, reflecting their different distances and orbital characteristics. Earth’s orbit is nearly circular, exhibiting a minor eccentricity of approximately 0.0167. Its distance from the Sun varies from 147,095,000 kilometers (0.983 Astronomical Units, AU) at perihelion (closest point to the Sun) to 151,930,000 kilometers (1.015 AU) at aphelion (farthest point). The average distance, also known as the semi-major axis, is 149,598,261 kilometers, defining one Astronomical Unit (AU).
Earth completes one orbit around the Sun in approximately 365.25 days, defining a year. This is equivalent to 1.000017 Julian years. The need to account for the extra 0.25 days every year leads to the introduction of a leap year every four years, where an extra day is added to the calendar. While a day is conventionally 24 hours, Earth’s sidereal rotation (rotation with respect to distant stars) is slightly shorter, at 23 hours, 56 minutes, and 4 seconds (0.997 Earth days). However, combined with its orbital motion, the time between sunrises (a solar day) averages out to 24 hours. From a vantage point above Earth’s celestial north pole, both its orbital motion and axial rotation appear counterclockwise. Earth’s axis is tilted at 23.4° relative to its orbital plane (ecliptic), causing seasonal variations on its surface due to varying amounts of sunlight received by each hemisphere throughout the year.
The orbits of the inner planets, including Earth, and Jupiter, highlighting the asteroid belt situated between Mars and Jupiter. Credit: Wikipedia Commons
Jupiter orbits the Sun at a much greater average distance of 778,299,000 kilometers (5.2 AU), ranging from 740,550,000 kilometers (4.95 AU) at perihelion to 816,040,000 kilometers (5.455 AU) at aphelion. At this distance, Jupiter takes a significantly longer time to complete one orbit, approximately 11.8618 Earth years. A Jovian year, therefore, is equivalent to 4,332.59 Earth days. However, Jupiter is the fastest rotating planet in our Solar System, completing one rotation on its axis in just under ten hours (9 hours, 55 minutes, and 30 seconds). Consequently, a Jovian year comprises a remarkable 10,475.8 Jovian solar days.
The banded appearance of Jupiter’s atmosphere, a result of its rapid rotation and atmospheric dynamics. Credit: NASA
Atmospheres: Layers of Air and Clouds
The atmospheres of Earth and Jupiter are fundamentally different in composition and structure. Earth’s atmosphere is composed of five primary layers: the Troposphere, Stratosphere, Mesosphere, Thermosphere, and Exosphere. Generally, air pressure and density decrease with increasing altitude. However, the relationship between temperature and altitude is more complex, varying across layers and even increasing with altitude in some cases. The troposphere, the lowest layer, contains approximately 80% of Earth’s atmospheric mass, with about 50% concentrated within the lowest 5.6 kilometers (3.48 miles), making it the densest layer. It is primarily composed of nitrogen (78%) and oxygen (21%), with trace amounts of water vapor, carbon dioxide, and other gases. Almost all of Earth’s atmospheric water vapor resides in the troposphere, making it the layer where most weather phenomena such as clouds, rain, snow, and storms occur. The exception is the thermosphere, where auroras, the Northern and Southern Lights (Aurora Borealis and Aurora Australis), take place.
Jupiter’s atmosphere, as mentioned earlier, is predominantly hydrogen and helium with trace amounts of other elements. Similar to Earth, Jupiter experiences auroras near its poles. However, Jupiter’s auroral activity is far more intense and almost perpetual. The intense radiation environment, Jupiter’s powerful magnetic field, and the influx of material from volcanic eruptions on its moon Io interacting with Jupiter’s ionosphere create a continuous and spectacular light show. Jupiter is also known for its dynamic and violent weather patterns. Wind speeds in zonal jets can reach 100 meters per second (360 kilometers per hour) and can peak at 620 kilometers per hour (385 miles per hour). Storms can form within hours and grow to thousands of kilometers in diameter overnight. The Great Red Spot, a colossal storm raging for at least 400 years, is a testament to Jupiter’s turbulent atmosphere. While the Great Red Spot has been observed shrinking and expanding over time, some predictions suggest it might eventually disappear.
Jupiter is perpetually shrouded in clouds composed of ammonia crystals and possibly ammonium hydrosulfide. These clouds are situated in the tropopause and are arranged in latitudinal bands known as “tropical regions.” The cloud layer extends to about 50 kilometers (31 miles) in depth and consists of at least two cloud decks: a dense lower deck and a thinner, clearer upper region.
Composite images combining data from Chandra X-Ray Observatory and Hubble Space Telescope, revealing Jupiter’s energetic x-ray auroras. Credit: NASA/CXC/UCL/W.Dunn et al/STScI
Evidence suggests a thin layer of water clouds may exist beneath the ammonia clouds, indicated by lightning detected in Jupiter’s atmosphere. Lightning is generated by charge separation caused by water’s polarity. Observations of these discharges indicate they can be up to a thousand times more powerful than lightning on Earth.
Moons: Solitary vs. a Crowd
Earth has a single natural satellite, the Moon. Its presence has been known since prehistoric times, deeply embedded in human mythology and astronomical traditions. The Moon significantly influences Earth’s tides and has been a focal point for scientific research and space exploration. Notably, the Moon is the only celestial body beyond Earth that humans have walked on. The first Moon landing occurred on July 20, 1969, with Neil Armstrong being the first person to step onto its surface. Since then, a total of 13 astronauts have visited the Moon, and their research has been crucial in understanding its composition and formation. Analysis of lunar rocks brought back to Earth supports the prevailing theory that the Moon formed about 4.5 billion years ago from debris ejected after a collision between Earth and a Mars-sized object named Theia. This collision created a debris disk around Earth, which eventually coalesced to form the Moon.
An illustration depicting Jupiter and its four largest moons, the Galilean satellites: Io, Europa, Ganymede, and Callisto. Credit: NASA
The Moon is one of the largest natural satellites in the Solar System and is the second densest among those with known densities (after Jupiter’s moon Io). It is tidally locked to Earth, meaning one side always faces our planet. The far side, often called the “Dark Side,” remained unseen until space probes photographed it.
In stark contrast, Jupiter boasts a vast system of 95 known moons (as of 2023, and constantly being updated with new discoveries). The four largest are the Galilean moons, discovered by Galileo Galilei and named Io, Europa, Ganymede, and Callisto. Io is the most volcanically active body in our Solar System. Europa is suspected to harbor a vast subsurface ocean, making it a prime target in the search for extraterrestrial life. Ganymede is the largest moon in the Solar System, even bigger than the planet Mercury. Callisto is also believed to possess a subsurface ocean and features some of the oldest surface material in the Solar System.
Beyond the Galilean moons, Jupiter has an Inner Group (or Amalthea group) consisting of four small moons: Metis, Adrastea, Amalthea, and Thebe. These moons are less than 200 kilometers in diameter, orbit within 200,000 kilometers of Jupiter, and have orbital inclinations of less than half a degree. Along with undiscovered moonlets, these inner moons contribute to and maintain Jupiter’s faint ring system. Jupiter also possesses a large number of Irregular Satellites, which are smaller and have more distant, eccentric, and inclined orbits. These irregular moons are grouped into families based on orbital similarities and are thought to be captured asteroids or fragments from collisions with larger captured objects.
In nearly every aspect imaginable, Earth and Jupiter represent planetary extremes. Despite extensive research, Jupiter continues to hold many secrets. Stay tuned to Universe Today for the latest discoveries from missions like NASA’s Juno, constantly providing new insights into this fascinating gas giant.
For more in-depth exploration of planets in our Solar System, check out our articles comparing Earth to Mercury, Venus, Mars, Saturn, and Neptune, as well as a comparison of Earth and the Moon.
Interested in learning more about Jupiter? Explore HubbleSite’s news releases about Jupiter and NASA’s Solar System Exploration Guide. Listen to Astronomy Cast’s podcast episode dedicated to Jupiter for even more fascinating facts.
