History of Solar System formation and evolution hypotheses moon and Mercury was a moon of Venus but drifted away because of the Sun's gravitational influence. Mars was a moon of Bellatrix. One major argument against exploding planets and moons is that there would not be an energy source powerful enough to cause such explosions. In J. Marvin Herndon's model, inner (large-core) planets form by condensation and raining-out from within giant gaseous protoplanets at high pressures and high temperatures. Earth's complete condensation included a c. 300 Earth-mass gas/ice shell that compressed the rocky kernel to about 66% of Earth's present diameter (Jupiter equates to about 300 Earth masses, which
Ring system Ring system A ring system is a disc or ring orbiting an astronomical object that is composed of solid material such as dust and moonlets, and is a common component of satellite systems around giant planets. A ring system around a planet is also known as a planetary ring system. The most prominent and most famous planetary rings in the Solar System are those around Saturn, but the other three giant planets (Jupiter, Uranus, and Neptune) also have ring systems. Recent evidence suggests that ring systems may also be found around other types of astronomical objects, including minor planets, moons,