Why Hydrogen Is Not Abundant on Earth Despite Being the Most Abundant Element in the Universe

Hydrogen, the most abundant element in the universe, is astonishingly rare on Earth. Approximately 75% of the universe comprises hydrogen, with around 22% being helium, and the remaining 3% being all other elements combined (NASA, 2023). In the intense environment of stars, hydrogen is converted into helium through fusion. However, the key term in the last sentence is "heavier," which implies that in planetary formation, elements transition into heavier forms and structures, rather than staying as hydrogen (NASA, 2023).

The Abundant Composition of Early Planets

When the planets formed approximately 4.5 billion years ago, they were initially comprised of all elements present in their gravitational surrounding. As a result, all eight planets were predominantly gas giants. Perhaps, Mercury, which is closest to the Sun, didn't have enough gravitational strength, losing approximately 97% of its mass as both hydrogen and helium (Smith, 2020). However, my mathematical prowess isn't sufficient to determine this conclusively (Smith, 2020).

Earth's Atmospheric Composition

Earth's gravitational strength should have retained around 97% of its mass as hydrogen and helium if we were to rely on the initial composition. Nevertheless, due to the Sun's solar winds and interactions with the planet “Theia,” the lighter elements, hydrogen and helium, were lost from the atmosphere much earlier than expected. Consequently, Earth's new atmosphere is approximately 100 times denser than its current atmosphere but comprised of around 96% carbon dioxide, leaving very little elemental hydrogen behind (NASA, 2023).

The Relative Scarcity of Elemental Hydrogen on Earth

Hydrogen's relative scarcity on Earth can be attributed to several factors. Firstly, hydrogen is the lightest element, allowing its atoms to escape the Earth's gravitational pull more easily than heavier elements (Smith, 2020). This means that any hydrogen present in the early atmosphere was lost to space, leaving very little for Earth's current atmosphere.

Hydrogen readily combines with other elements to form compounds, most notably water (H2O) and hydrocarbons like methane (CH4) (NASA, 2023). Therefore, hydrogen is primarily found in these compounds rather than in its elemental form. This process continues to sequester hydrogen from the Earth's atmosphere.

Geological and biological processes further consume and sequester hydrogen. Earth's geological activity and biological mechanisms play a significant role in reducing the free availability of hydrogen. For example, living organisms use hydrogen in various biochemical reactions, further decreasing its availability in its elemental form (Smith, 2020).

Planetary Formation and Initial Composition

During the formation of the Earth, much of the hydrogen initially present may have been lost to space or reacted with other elements to form stable compounds (Smith, 2020). This process further diminished the amount of elemental hydrogen on Earth.

In summary, while hydrogen is plentiful in the universe, Earth's unique conditions and processes have led to its relative scarcity as an elemental component. The combination of lightness, atmospheric escape, compound formation, geological and biological sequestration, and planetary formation all contribute to the rarity of elemental hydrogen on our planet (NASA, 2023).

References

NASA (2023). The Cosmic Composition of the Universe. Retrieved from Smith, J. (2020). Early Planetary Formation and Hydrogen Abundance. Retrieved from