The “unexpected” discovery of Liège researchers reinforces the idea of ​​extraterrestrial life and “turns the prevailing theory upside down.”

Until now, it was thought that water on rocky planets (such as Earth) is very scarce. But, through our studies, we now have this evidence that water may be more common than we thought on this type of planet. This motivates this search for biosignatures (chemical effects that can only be explained by life, editor’s note) on planets other than EarthValentin Christians, FNRS researcher at ULiège and co-author of this discovery, which was published in nature.

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Concretely, the international research group Minds, which includes researchers from ULiège, using the famous James Webb telescope, observed the young star PDS 70 at a distance of 370 light years from us. Scientists have detected traces of water in the inner region of the disk of gas and dust surrounding the star. Essentially, these so-called stellar disks give rise to planets orbiting the star when the material of these disks gradually clumps together.

The cradle of the planets

Therefore, astronomers expect terrestrial planets to form in this region. The researchers’ discovery suggests that any rocky planet that forms there would thus benefit from having a large local reservoir of water at its disposal, improving the chances of life later appearing. “The fact that these traces of water were found in a rocky planet-forming disk, which is completely evolved and completely prototype, suggests that this presence of water could be more common than expected so far.Valentin Christians, who adds that this discovery “exceptional “ poses too “The first detection of water in a relatively well-developed disk and the first detection of water in a planet-forming host disk”.

The discovery also calls into question another generally accepted theory: how water got to our planet. Until now, scientists’ preferred mechanism for supplying water to rocky planets is the bombardment of the asteroids themselves that carry water.

“It is possible that extraterrestrial civilizations exist, and that they are very numerous and very diverse.”

“Our discovery somewhat upsets the view of the evolving protoplanetary disks as ‘dry’ and thus challenges the prevailing theory, the hypothesis that water is supplied to rocky planets only by subsequent bombardment by water-bearing asteroids, Valentin Christiaens resumes. For the Earth, it is believed that there are several sources of water, but in fact it is possible that meteorite bombardment is not the dominant mechanism for this water supply on Earth and that water was present at the time of the formation of our planet.

What is the origin of the water in PDS 70?

And the scientist continues: while studying the PDS 70 disc,“We didn’t expect to find water there because rocky planets like Earth form close to their star. The star’s ultraviolet rays tend to break up water molecules. So we’ll be looking at different ways to understand how this water manages to stay close to the star.”

Researchers are already putting forward various hypotheses to explain the origin and presence of water in this place. One possibility is that the water is the remnant of an initially water-rich nebula that predates the disk phase. Water is very common in this type of nebula, especially in the case of ice, as it coats tiny particles of dust. When exposed to heat near a forming star, the water evaporates and then mixes with other gases. Unfortunately, water molecules are very fragile and break down into smaller components such as hydrogen and oxygen when exposed to harmful ultraviolet radiation from a nearby star. However, surrounding materials such as dust and water particles can act as a protective shield. Therefore, it appears that some of the water discovered near PDS 70 escaped this destruction.

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Under certain conditions, oxygen and hydrogen can combine to form water vapor. If the temperature conditions and gas density are right, water vapor can form at the site, in the inner disk, and compensate for the destruction by the star’s ultraviolet radiation.

In addition, another source of water vapor could come from the ice-rich dust particles initially present at the outer edges of the disk. The friction of ice-rich dust against the rotating gas in the disk can cause these particles to slide down from the outer edges of the disk inward. When dust grains enter the inner disk, near the star, the ice then turns into gas.

“Perhaps the truth lies in a mixture of all these options, for examplesays researcher Julia Perotti (Max Planck Institute), co-author of the study. However, it is likely that one mechanism plays a more critical role than others in maintaining the water reservoir of the PDS 70. The task ahead will be to find out by which mechanism it operates.”