The Earth's Mass: A Slow, Continuous Journey of Gain and Loss

On a grand scale, the Earth is experiencing a continuous process of gaining and losing mass. This article explores the dynamics of how Earth's mass changes over time, focusing on both the accumulation and attrition of matter involved in this fascinating phenomenon.

Accretion and the Gain in Earth's Mass

Earth's mass is constantly increasing through a process known as accretion, a term that describes the gradual growth of a body by the collection of matter. According to scientific sources, Earth gains approximately 40 million kilograms per year through the ingestion of meteors, asteroids, and cosmic dust. This process, though seemingly insignificant on a daily basis, has a considerable impact over geological timescales. For instance, if current accretion rates were to continue, it would take approximately 150 million billion years to double the Earth's size. This increase in mass is primarily due to the accumulation of matter from extraterrestrial sources.

The Loss of Earth's Mass: Atmospheric Degradation

Contrary to the increase in mass from accretion, Earth also loses mass through the loss of atmospheric gases. This is a more subtle and gradual process that has been ongoing for eons. The Earth loses about 3 kilograms of hydrogen and traces of helium every second. Hydrogen is primarily lost through various natural processes including the weathering of rocks, while helium is a byproduct of radioactive decay. Given the vastness of the Earth's atmosphere, which weighs approximately 5 x 10^15 tonnes, the loss of 3 kg every second may seem concerning; however, the scale of this loss is minor when compared to the total mass of the Earth.

Balancing Act: The Role of Cosmic Dust and Meteorites

To understand the net effect on Earth's mass, it is crucial to consider the balance between the loss of atmospheric gases and the gain from cosmic dust and meteorites. Cosmochemists estimate that about 100,000 tonnes of cosmic dust fall onto Earth each year, contributing to the increase in mass. Meanwhile, the contribution from meteorites is less significant but still measurable, with about 15,000 tonnes added annually. Despite the rare occurrence of massive meteorites, the majority of the matter added to the Earth's mass comes from cosmic dust, primarily because larger meteorites are exceedingly rare.

Conclusion: The Overall Impact on Earth's Mass

While the Earth is indeed gaining and losing mass, the net effect over short periods is a gradual decrease in mass due to atmospheric loss. However, this loss is compensated by the continuous influx of cosmic dust and meteorites, keeping Earth's mass in a relative state of balance. Although this process occurs over extremely long periods, the Earth remains stable and habitable for the foreseeable future. Therefore, there is no immediate cause for concern regarding changes in Earth's mass.