When the first raindrop falls on Earth, people react differently: children run to the roof to swim; farmers look up in hope; and streets fill with water. However, they rarely think about what the first rain on the planet was like. At that time, there were no people, no plants, no cities, and no living beings capable of feeling the rain. The Earth itself looked different—it was surrounded by scorching rocks, volcanoes, and a vapor atmosphere. Nevertheless, on this boiling Earth, drops of water began to fall from the sky one day. But when exactly did this event happen? Do scientists have any evidence of the first rain on Earth?
The answer to this question was found in a very small stone, which is about 4 billion years old. A study published in 2024 provided evidence that the water cycle, associated with rain and fresh water, was already functioning during the early history of Earth. That is, the history of rain, which we consider a normal weather event today, could be recorded in the earliest chapters of the planet's history.
The formation of Earth occurred approximately 4.54 billion years ago. Initially, it bore little resemblance to today's beautiful blue planet. Its surface was extremely hot, and active volcanoes were everywhere. The early atmosphere of Earth contained many gases. Volcanic activity contributed to the release of large amounts of water vapor into the atmosphere. As the temperature began to drop, the water vapor in the atmosphere condensed, forming clouds, and then the water fell as drops onto the Earth's surface. This process laid the foundation for the water cycle on Earth.
But how did scientists find this out? Here, the story becomes even more interesting. In 2024, an international team of scientists, including specialists from Curtin University, studied ancient zircon crystals found in the Jack Hills area in Western Australia. These crystals are billions of years old and have preserved chemical traces of that atmosphere.
Scientists analyzed the oxygen isotopes contained in these zircon crystals. The study revealed signs that about 4 billion years ago, fresh water was present on the Earth's surface, interacting with rocks. This meant that by that time, Earth not only had water but also processes similar to the water cycle had begun. This study was published in the journal Nature Geoscience in June 2024.
Scientists do not possess a single drop that can definitively be called the first raindrop on Earth. However, isotopic traces in ancient zircon crystals indicate that the rain-related water cycle may have been active about 4 billion years ago or even earlier. According to the study, contact between fresh water and the continental surface began approximately 4 billion years ago.
Thus, the history of rain, which we perceive as an everyday thing, began at the very beginning of Earth's history.
This raises the next question: where did such water come from? In early Earth, water vapor entered the atmosphere due to volcanic activity. Additionally, asteroids and other bodies from the early solar system may have contributed to Earth's water reserves. When the Earth cooled and rain began, the water collected in rocks, depressions, and lowlands. Over time, the rain continued, the water flowed, and water sources formed in different parts of the Earth. Gradually, large bodies of water developed, leading to the beginning of the process of forming seas and oceans.
The most fascinating thing is that the rain brought to Earth not only water. Water played a huge role in creating the conditions necessary for life. In the 2024 study, scientists also noted that the presence of a continental surface, fresh water, and the water cycle on early Earth could have contributed to the formation of a favorable environment for life.
Imagine: the roots of the rain under which we walk with an umbrella today are hidden in the era of about 4 billion years ago, when there were no signs of life on Earth. Back then, no one saw the first drop falling from the sky. But this water gradually accumulated, seas formed, the water cycle worked, and after billions of years of this long history, life blossomed on Earth. Therefore, the first rain on Earth was not just water falling from the sky; it was the beginning of the blue planet we call home today.
