Question

Light elements like hydrogen and helium form a large percentage of the outer planets and Sun is made up primarily of hydrogen. Why are these elements nearly absent from the inner planets?

Answer 1

Answer:

Instead of Helium and Hydrogen there are heavier elements in inner planets like Nitrogen and oxygen.

Explanation:

• As the inner planets like Mercury, Venus and Mars and earth have a solid surface which is separated by the Sharpe atmosphere, and their gravity is too low to hold these light gases.

• Uranus is primarily composed of gases and ice of which 83% is hydrogen and 15% helium and rest are trace gases. As in the early composition of the atmosphere, the inner planets like the earth had a solid atmosphere composed of solid silicates elements like magnesium, iron, calcium, and potassium.  

• As the earth has a highly unstable atmosphere only carbon, nitrogen and oxygen combined in lightning occur. And planet mercury has no atmosphere thus gravity is too low to hold any gas.