A planetary collision struck life into the Earth, reveals new study

Before becoming the only planet in our solar system teeming with life, Earth was a desolate, stony globe — dry as dust and chemically imperfect.

A new study from the Institute of Geological Sciences at the University of Bern, Switzerland, has traced the planet's early chemical history with remarkable precision, finding that the proto-Earth's composition was finalised within three million years of the Solar System's formation.

Early Earth lacked the very chemicals required for life. Water, carbon molecules, and other volatile components were absent from the mixture. According to the researchers, a cosmic collision, most likely with a planet named Theia, provided the missing elements and changed Earth into the life-friendly blue planet we call home today.

The inner Solar System, which includes Earth, was too hot for volatile elements to condense and integrate into planets; therefore, the proto-Earth began as a barren rock. Only bodies that formed farther from the Sun, in cooler zones, could amass these life-sustaining components, Asianet writes.

The researchers used isotopes in meteorites and terrestrial rocks to reconstruct the chronology of Earth's early chemistry. Using manganese-53 decay as a precise "clock," scientists found that the proto-Earth's chemical signature evolved in less than three million years — a surprisingly rapid process on the cosmic scale.

The major turning point occurred when the proto-Earth collided with Theia, a Mars-sized planet that most likely evolved in the colder, outer Solar System. This impact introduced water and volatile molecules to Earth, allowing it to host life. Without this accidental event, Earth could have remained a lifeless, arid world — and we wouldn’t have been here to wonder where we came from!

“Earth’s habitability was not guaranteed,” explains Dr Pascal Kruttasch, lead author of the study, adding, “Life-friendly conditions depended on a rare cosmic event, highlighting how delicate the balance is for planets to become suitable for life.”