Is there a reason why we have four “rock” planets lined up followed by four “gas” planets in a row, or is it merely coincidence?

Question

Is there a reason why we have four “rock” planets lined up followed by four “gas” planets in a row, or is it merely coincidence?

In: Planetary Science

Answer 1

In some groups theirs 2 gas giants and 2 ice giants. Neptune and Uranus are different from Saturn and Jupiter. Saturn and Jupiter are mostly hydrogen and helium. Neptune and Uranus are only 20% hydrogen and mostly heavier materials like oxygen and ammonia.

So it may be 4 terrestrial, 2 gas giants, and 2 ice giants.