[Reading Science] Has Water Existed on Earth Since the Beginning?

JWST Observes Water Vapor in Rocky Planet Formation Region
Survives Hot Temperatures and Stellar Winds Contrary to Previous Theories
May Be Indirect Evidence Supporting Earth's Water Self-Generation Theory

Water is an essential element for life on Earth. However, no one knows exactly when or how water came to exist on Earth. There are only two main theories: the external influx theory, which suggests water came from comets and asteroids, and the in-situ formation theory, which proposes water existed from the very beginning. What is certain is that Earth is located at an appropriate distance from the Sun, in the so-called Goldilocks zone, allowing water to be preserved and enabling life to flourish. Recently, the James Webb Space Telescope (JWST), often called 'the eye of humanity,' has attracted attention by producing observational results that support the in-situ formation theory. Water was detected in a distant stellar system where Earth-like planets are being formed, still filled with gas and dust. This suggests that Earth may have contained water from its earliest formation stages.

An artist's impression of the PDS 70 star system where JWST observed the presence of water vapor. Photo by NASA website

The U.S. National Aeronautics and Space Administration (NASA) announced on the 24th (local time) that a research team composed of the Max Planck Institute for Astronomy (MPIA) in Germany and others analyzed data captured by JWST's Mid-Infrared Instrument (MIRI) and confirmed the presence of water vapor in the young stellar system 'PDS 70,' located about 370 light-years from Earth. This stellar system is currently in the process of star formation. It has an inner disk and an outer disk made of gas and dust, separated by approximately 8 billion kilometers. Between these two disks, two already formed gas giant planets exist.

The research team detected water vapor in the rocky region about 160 million kilometers from the central star within the inner disk of this stellar system, where Earth-like planets are presumed to be forming. While water has been observed in disks of other stellar systems before, this is the first time it has been detected in a region where rocky planets similar to Earth are actively forming.

Julia Perotti, a researcher at MPIA, told NASA, "Water has been found in other disks, but not this close to the center, nor in a stellar system where planets are just beginning to form. This observation was not possible before the launch of the Webb telescope." Thomas Henning, director of MPIA, also explained, "This discovery is very interesting because it investigates the typical locations where rocky planets similar to Earth are generally formed."

The PDS 70 star where this discovery was made is classified as a 'K-type star,' which is cooler than the Sun. It is estimated to have formed about 54 million years ago. Compared to stars with disks at other stages of planet formation, this is relatively old. NASA explains that this makes the discovery of water vapor even more remarkable. During the planet formation stage, gas and dust decrease over time because they are either blown away by the radiation heat or stellar winds from the central star or clump together to form larger bodies that eventually become stars. Water behaves similarly. Astronomers have long believed that water cannot survive the harsh stellar radiation, creating a dry environment where rocky planets form.

So far, planets formed within the inner disk of the PDS 70 stellar system have not been discovered. However, components that make up rocky planets, such as silicates like those on Earth, are present. Finding water vapor under these conditions suggests that rocky planets like Earth may contain water from their earliest formation stages.

Then, where did the water in the PDS 70 stellar system come from? One plausible hypothesis is that it was there from the beginning. Water molecules could have been formed in situ through the fusion of hydrogen and oxygen atoms. Another possibility is that frozen cosmic dust molecules from the colder outer disk migrated to the warmer inner disk, where the ice melted and turned into water vapor.

Questions also arise about how water can remain so close to a star. Generally, a star's intense ultraviolet radiation destroys and disperses any form of water molecules. NASA speculates that cosmic dust and other water molecules surrounding the water vapor acted as a protective shield, allowing the detected water vapor to be preserved. NASA stated, "The research team plans to conduct additional observations of the PDS 70 stellar system using the Near-Infrared Camera (NIRCam) and Near-Infrared Spectrograph (NIRSpec)."