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Study: The water cycle is older than previously thought

Study: The water cycle is older than previously thought

As of: June 23, 2024 at 11:00 AM

Evaporation, condensation and precipitation – according to a study, the water cycle on Earth has been longer than previously thought. It is also possible that life on Earth arose earlier.

Written by Nicholas Hillebrand and Martina Janning, SWR

The water cycle, including rain, is the basis of life on Earth – and perhaps even the origin of life itself. By examining ancient rock samples, a research team from Abu Dhabi has now found that the water cycle is evaporation, clouds and precipitation. At least 500 million years older than previously assumed. They have now published the results in Journal of Natural Earth Sciences.

Without water, our Earth would be a barren place: there would be no life – no single-celled organisms, no plants and no animals. It is not known exactly where and how life first arose. But one thing is clear: water played a crucial role.

Did rain enable life to appear on Earth?

According to one theory, the first organisms arose in the deep sea, in mineral-rich hot springs called black smokers. Another theory suggests that life could also have originated in small pools on Earth – fresh water perhaps mixing with gases from the Earth's interior, thus providing a fertile breeding ground for protozoa.

For the first prehistoric creatures to exist in bodies of water on land, water had to be available there as well. In the past, as now, this was only possible through the water cycle including rain.

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Water Cycle 500 million years older than previously thought

The first discoveries indicating life in small bodies of water on Earth are It is about 3.5 billion years old. Accordingly, experts assumed that it would rain on Earth at this stage at the latest. However, there has long been uncertainty among experts about exactly how long the rain fell.

A research team from Abu Dhabi, Australia and China have now found evidence that the water cycle could be at least four billion years old, 500 million years older than previously thought.

Zircon crystals are ancient witnesses

Researchers examined rock samples from the Jack Hills Mountains in Western Australia. The world's oldest mineral grains can be found here: zircon crystals. With the help of these grains, which are up to 4.4 billion years old, they were able to reconstruct the chemical composition of the Earth at that time in order to better understand the geological conditions.

To do this, the researchers irradiated the grains with ions, causing them to release particles of zirconium grains. These separated particles were then detected by a detector so that the exact molecular structure of the crystals could be determined. This, in turn, provided information about the composition of the magma that emerged underground more than four billion years ago and from which crystals were formed once the magma cooled in contact with water.

Crystals show Earth's early fresh water supply

Oxygen molecules trapped in crystals are of particular interest to researchers. These so-called isotopes come in two different versions with different weights. Depending on whether the rising magma comes into contact with fresh or salty water, the ratio of heavy and light oxygen isotopes within the crystals also changes.

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Analysis of the data eventually showed that at least four billion years ago there were freshwater deposits in the land areas of Earth that the rising magma came into contact with. This indicates that it must have already rained at that time to replenish the Earth's fresh water reservoirs.

The results not only provide evidence that the water cycle on Earth began much earlier than previously demonstrated, but also provide evidence that land masses containing reservoirs of fresh water existed earlier than previously thought. This, in turn, suggests that life on Earth may have originated earlier, and that it may have originated in water on land rather than in the sea. However, other geological evidence is missing to reinforce this thesis.