Earth's Spheres and the Origin of Life: A Deep Dive

Earth's Spheres

Earth Subsystems

Atmosphere: The external layer of the planet in a gaseous state.

Hydrosphere: The discontinuous layer that surrounds the Earth's surface with water. Liquid water is fundamentally found under the surface, in continents and oceans. Although in small quantities, glacial ice is the first part of the atmosphere for living beings.

Geosphere: The rocky structure that makes up the Earth system's greatest volume. We will focus on its most external part, the lithosphere.

Biosphere: The system made up of living beings that inhabit the Earth. It occupies the lower part of the atmosphere, the upper part of the lithosphere, and the hydrosphere.

The Gaia Hypothesis

1. The biosphere is an entity whose main properties are the sum of the properties of its parts.
2. The biosphere acquired the capacity to control the global environment according to its needs.
3. The biosphere has conditioned the planet's air and has the ability to regulate processes related to life.
4. Gaia is a cybernetic biological system with homeostatic tendencies (it tends to maintain a stable state).

Origin of the Earth

The Earth originated 4.6 billion years ago, along with the other planets of the solar system, from small bodies of solid accretion called planetesimals.

Changes in the Atmosphere and Climate

As a consequence of volcanic eruptions, the geosphere emitted volatile compounds whose accumulation led to the primitive atmosphere, rich in gases such as nitrogen, methane, ammonia, and water vapor. One of the main causes of climate change was the appearance, about 2 billion years ago, of living beings that had two extremely important consequences:

• Transformation of the reducing atmosphere into an oxidizing one.
• Formation of the ozone layer in the stratosphere, which acts as a protective screen against high-energy radiation, enabling the development of life outside of water.

In the early stages of the Earth, water would be found in the atmosphere as vapor. When the planet cooled during its formation, about 10-20 million years ago, generalized condensation and the formation of the oceans occurred. The primitive oceans, rich in organic compounds of abiotic origin, experienced changes due to multiple factors.