The Transformative Collision: How an Ancient Cosmic Event Shaped Earth's Habitability

The Earth we inhabit today may not be the same planet that came into existence 4.5 billion years ago. A significant number of scientists postulate that during its nascent stage, Earth collided with another celestial body approximately the size of Mars. Instead of being obliterated, this collision led to a profound transformation. Earth incorporated the mass of this foreign entity, evolving into the planet we recognize today. Recent research has further enhanced the significance of this hypothesized cosmic event: Scientists contend that without this other body, the fundamental conditions for life to emerge on Earth might never have materialized.

The Proto - Earth's Volatile Element Loss

A research team from the University of Bern in Switzerland posits that due to its close proximity to the Sun, the proto - Earth, which existed prior to this potential collision, lost the volatile elements crucial for the formation of complex molecules. Their analysis indicates that any hydrogen, carbon, or sulfur evaporated within merely the first 3 million years after the proto - Earth's formation. Thus, they suggest that if Earth had evolved without external contributions, it would likely be a drier planet, far more inhospitable to the development of complex life forms.

The Role of an Extraterrestrial Impact

Conversely, if a body formed in the outer regions of the solar system - a region known to produce rocks rich in water and other volatile elements - and subsequently collided with a rocky planet like the proto - Earth, this could have provided the unique chemical richness characteristic of our planet today, even after Earth's initial intense evaporation process. This hypothesis aligns with other propositions suggesting an extraterrestrial origin of water, according to which icy meteorites bombarded the primitive Earth, depositing their molecules.

Isotope Analysis: Unveiling the Past

In a study published in Science Advances, researchers accurately measured the radioactive decay of two isotopes, manganese - 53 to chromium - 53, in both terrestrial samples and meteorite fragments found on Earth. Since these space rocks formed simultaneously with the Sun and the planets of the solar system, analyzing their traces and composition is tantamount to opening a time - capsule from the past. By calculating the radioactive decay of manganese - 53, the researchers were able to determine the point in time when the planets ceased exchanging material with their environment and retained the chemical elements they would possess indefinitely.

Insights from Isotope Ratios

Their findings reveal that the proto - Earth sealed its elements just 3 million years after the birth of the solar system. Additionally, they discovered that the early planet had a very low ratio of manganese to chromium, indicating that the proto - Earth was an extremely hot world capable of expelling manganese. Given that this element is less volatile than other more vital elements such as hydrogen, carbon, or sulfur, these elements must have also escaped.

Theia: The Catalyst for Life?

“Thanks to our results, we know that the proto - Earth was initially a dry rocky planet. It can therefore be assumed that it was only the collision with Theia that brought volatile elements to Earth and ultimately made life possible there,” stated Pascal Kruttasch, the lead author of the report, in a University of Bern press release. Theia is the name assigned to the hypothetical body believed to have collided with the proto - Earth approximately 4.5 billion years ago. The researchers surmise that this impact occurred between 30 and 100 million years after the inception of the solar system - that is, several tens of millions of years after the ancestor of our planet was known to be a parched world.

The Gap Between Volatiles and Life

However, the arrival of water and other volatile elements does not directly translate to the immediate emergence of life. While water alone does not generate life, it does create a much more conducive chemical and physical environment for the appearance of other molecules and, consequently, the biological processes that form the basis of cells. In this context, Theia set the stage but did not trigger the spark of life.

This article originally appeared on WIRED en Español and has been translated from Spanish.