Why did Earth's earliest atmosphere, composed primarily of hydrogen and helium, NOT last long?
A) Hydrogen is highly reactive, and it soon became bound into chemical compounds in Earth's rocks.
B) Hydrogen and helium are light gases, and they soon escaped into space.
C) Biological activity very quickly combined the hydrogen with oxygen to form water.
D) The hydrogen soon became dissolved in Earth's oceans.

Question

Quizplus · Accepted Answer

Hydrogen and helium are the lightest elements, making them unable to be retained by Earth's gravity, especially in the absence of a strong magnetic field and thicker atmosphere, leading to their escape into space.

Why Did Earth's Earliest Atmosphere, Composed Primarily of Hydrogen and Helium