It exploded about 3,200,000 years ago, spewing out comets and asteroids. Many fragments collided with other planets and moons, explaining why some planets and moons are cratered primarily on one side. This theory also explains the origin of asteroids and some similarities between comets and asteroids. Volcanic Eruption Theory. Jupiter's large, recent family suggests that Jupiter was the most recent planet to erupt.
Giant planets are huge reservoirs of hydrogen, a major constituent of comets.
New comets continuously replenish those being rapidly lost through collisions with planets or moons, evaporation when passing near the Sun, and ejection from the solar system. Oort Cloud Theory. Stars passing near the solar system perturbed parts of this Oort cloud, sending randomly oriented comets on trajectories that pass near the Sun. This is why calculations show so many longperiod comets falling into the center of the solar system from about 50,000 AU away. If energy is added, the comet is usually thrown from the solar system on a hyperbolic orbit.