What are some of the similarities and differences between the inner planets and outer planets?

1 Answer
Apr 9, 2016

Inner planets have solid rocky cores, outer planets are mostly gas. Similar in that they are all part of our solar system.


The inner planets (Mercury, Venus, Earth, Mars) formed by accretion from heavy elements like iron, nickel, and silica. Thus, they tend to have solid core, mantel and crust to them. Relative to the gas giants, they also tend to be smallish in size. Earth at least is also in the Goldilocks zone for water to stay liquid - not too hot and not too cold. Liquid water is a precursor for life to evolve.

The outer planets, Jupiter and beyond mostly consist of the lighter elements of hydrogen and helium. They may have small rocky cores to them. like the inner planets. When the hydrogen in the sun collapsed to actually start nuclear fusion, a huge solar wind blew remaining hydrogen to the outer regions of the solar system and it collapsed into the outer planets.

One interesting theory is that if the amount of hydrogen in the outer planetary realm was a bit larger, a second binary star would likely have formed instead of the outer gas giant planets. If a binary star system had formed, its unlikely that life on Earth would have evolved,