If a terrestrial, rocky planet like Earth were scaled up to possess the size and mass of Jupiter, the resulting world would be a “Mega-Earth” or “Super-Jupiter.” This thought experiment forces us to confront the extreme limits of planetary physics, orbital mechanics, and biology. Such a colossal terrestrial body would fundamentally alter every characteristic we associate with our home world. It would face immense internal pressures and external gravitational consequences, creating an environment unrecognizable and hostile to Earth-like conditions.
Surface Gravity and Planetary Compression
The most immediate consequence of this scaling is the colossal increase in surface gravity. Jupiter is 318 times more massive than Earth. If a rocky planet maintained Earth’s density while expanding to Jupiter’s radius, its surface gravity would be approximately 11 times that of Earth’s. However, a rocky body of Jupiter’s size would be far denser due to internal compression, resulting in a mass that could easily exceed 1,000 Earth masses. The surface gravity on this hypothetical rocky Jupiter would likely be tens, or even hundreds, of times stronger than Earth’s, pinning down anything on its surface.
This immense mass creates extraordinary pressures deep within the planet, fundamentally changing the internal structure. The pressure at the core-mantle boundary would be well over 10 times that of Earth’s, potentially reaching 10 terapascal (TPa). These extreme pressures would compress silicates, the main component of rock, into exotic, high-pressure phases. The entire mantle would become far more rigid and dense, potentially solidifying much of the interior.
Leaving such a planet would be almost insurmountable due to the enormous escape velocity. Jupiter’s current escape velocity is 59.5 kilometers per second, compared to Earth’s 11.2 kilometers per second. For a denser, rocky planet of Jupiter’s size, the escape velocity would be significantly higher. This would require an exponentially greater amount of energy to launch any object into orbit or beyond.
Atmospheric and Geological Extremes
The massive increase in gravity would dramatically affect the planet’s envelope of gases. The powerful gravitational field would retain much lighter, more volatile gases, such as hydrogen and helium, which Earth’s lower gravity allows to escape. This retention would result in an incredibly thick, dense atmosphere, leading to crushing atmospheric pressure at the surface. The pressure could be so extreme that the atmosphere near the ground might transition into a supercritical fluid, where there is no distinction between liquid and gas.
The profound internal compression would also have a devastating effect on the planet’s geology. The extremely high internal pressure and the resulting rigidity of the mantle would likely prevent the large-scale movement of tectonic plates. The planet would transition into a “stagnant lid” regime, where the lithosphere is a single, unbroken shell covering the entire world. This halts the continuous recycling of crustal material responsible for Earth’s volcanoes and earthquakes.
A geologically dead planet would result, lacking the volcanism and plate tectonics that regulate the global carbon cycle on Earth. The planet’s sheer mass and resulting compression would generate immense internal heat. This heat, combined with the atmospheric blanketing effect of the dense air, could contribute to extremely high surface temperatures. This makes the environment hostile even before considering sunlight.
Celestial Mechanics: The New Solar System Dynamics
A Jupiter-mass Earth would completely destabilize the delicate balance of the Solar System. The Sun and Earth currently orbit a common center of mass, or barycenter, deep within the Sun’s interior. With Earth’s mass increased to that of Jupiter, the Sun-Earth barycenter would shift to a point just outside the Sun’s surface. This would force the Sun to “wobble” much more dramatically.
This new, massive Earth would exert significantly increased tidal forces on its moon. The Moon’s current orbit would likely become unstable. The increased gravitational pull could either tear the Moon apart or send it spiraling into an extremely low orbit. The powerful gravitational influence of the new Earth would also cause substantial orbital perturbations for the other inner planets, Venus and Mercury.
The entire inner Solar System would become a much more chaotic environment. The gravitational resonance issues caused by such a massive terrestrial body could potentially destabilize the orbits of Mars and the asteroid belt over long timescales. The new gravitational landscape would be dominated by this rocky giant, fundamentally reshaping the orbital paths of every nearby celestial body.
Biological Constraints on a Super-Earth
Life as we know it would face nearly insurmountable challenges under these conditions. The physiological limits of complex, upright life are quickly exceeded under hypergravity, as large terrestrial organisms are tuned to one Earth gravity. Under a gravity tens of times stronger, the compressive strength of bones would be tested, and the sheer weight would cause circulatory systems to fail. Long-term survival for complex organisms like mammals or trees would be structurally and metabolically impossible, as the forces would crush skeletal structures.
If any life could manage to survive, it would need to possess a radically different biophysics. Potential life forms would likely be very small, flat, or perhaps entirely water-based, using buoyancy to counteract the immense weight. Microorganisms, such as bacteria, have been shown to survive and even thrive under artificial hypergravity forces. This suggests that life might be relegated to the microbial level, existing as extremophiles adapted to the crushing pressure and gravitational constraints.