The two most abundant elements in the universe are hydrogen and helium, which account for less than 1% of what is found on Earth due to various reasons.
On a cosmic scale, hydrogen is abundant primarily because a significant amount of this element was formed during the Big Bang, according to IFL Science. In the first moments after its inception, the universe was a mass of quarks and gluons. Once things stabilized, most observable matter consisted of electrons, protons, and neutrons, along with some more exotic subatomic particles. Electrons and protons commonly combine to form hydrogen. A small amount of helium and even less lithium were also produced. Most primordial lithium was destroyed in stars, but these same stars fuse hydrogen to create helium and other elements in the periodic table at the end of their life cycle.
Helium on Earth is primarily the result of radioactive decay deep within the planet. (Photo: Newsweek).
However, on Earth, the ratio of hydrogen to oxygen in the oceans is 2:1 (with sodium, chlorine, and salt-forming elements coming from other sources). Some of it binds to rocks or carbon molecules such as methane in the atmosphere. Nevertheless, in terms of atomic ratio on the planet, there is not much hydrogen. Helium is even much rarer, to the point that it went unnoticed until its spectral line was discovered during a solar eclipse.
Like all planets, Earth formed from a protoplanetary disk made up of hydrogen and helium from the Big Bang, along with a few heavier elements fused in early stars and spread throughout the galaxy in supernova explosions and kilonovae. The Sun and the gas giant planets in the system reflect this composition, although most of the Sun’s original hydrogen has since transformed into helium. Earth and the inner planets of the system are entirely different.
Besides being abundant in the universe, hydrogen and helium are similar in that both are very light gases, meaning they can easily escape Earth’s gravitational pull. Larger planets like Jupiter retain more hydrogen and helium due to their immense gravity, whereas Earth’s gravitational force is insufficient. Moreover, Earth is much closer to the Sun than many gas giants. The gases become warmer, gain more energy, and increase the likelihood of escaping.
Helium is particularly rare because it is an inert gas. It rarely combines with any other atoms that could hold it tightly enough to prevent escape. Most planetary scientists believe that the original helium from the protoplanetary disk no longer exists on Earth. The helium we have primarily results from the radioactive decay of heavier elements. A common form of decay includes the production of alpha particles, which consist of two protons and two neutrons bonded together to form a particle identical to the nucleus of a helium-4 atom. After being released, alpha particles can attract electrons from their surroundings to form helium.
If released near the surface, helium atoms are likely to rise into the atmosphere and then drift into space. However, helium produced from radioactive activity deep within the Earth can become trapped inside caverns.
Although helium is often associated with balloons, it has many more important applications, such as cooling scientific equipment and magnetic resonance imaging devices to temperatures too cold to use alternatives like liquid nitrogen. The helium reserves depend on drilling areas where helium has accumulated over millions of years. Most helium reserves are collected as a byproduct when drilling for methane.
Hydrogen on Earth is more abundant than helium because it readily bonds with elements such as oxygen. A water vapor molecule weighs nine times more than an H2 molecule, making hydrogen less likely to escape. However, most of the hydrogen in the planetary microcosm that formed Earth has disappeared long ago, especially when collisions turned the planet’s surface into a magma sea.
