The James Webb Space Telescope found a key clue about the origin of the Earth

The various processes that lead to the formation of rocky planets are relatively well known today. However, certain points remain on which there is still no real consensus, especially regarding the very beginning of the process. Current models suggest that the story begins with some kind of seed around which the material will subsequently agglomerate. But the exact nature of this seed remains quite mysterious.

Frozen adventurers on the planet’s origin

One of the most promising theories is that planet formation begins with small chunks of ice-covered rock that populate the exterior of protoplanetary disks — circular clumps that contain the material that feeds new planets.

Under the action of friction with the surrounding material, they then float away towards the hot region surrounding the young star. When they got close enough, rrelease water vapor which plays an important role in the rest of the process. This is a solid hypothesis, but one that no one has been able to confirm, because no instrument has ever been able to document this dynamic.

However, that just changed thanks to The James Webb Space Telescopeand this discovery offers a a new view on the formation of terrestrial planets like Earth.

Compact discs are more loaded with water

It all started with the observation of four protoplanetary disks — two quite compact and two very extensive. They circled stars from the same family as the Sun. The difference is that these stars were all 2 to 3 million years old, compared to about 4.6 billion years for our favorite star. So it was about child stars.

In theory, the motion of ice rocks should be greater in the central regions of the most compact discs but in extended disks.

This hypothesis stems from the fact that larger discs tend to be cut into several different zones according to the areas where the pressure is higher. Researchers call them pressure traps. These correspond to the darker areas to the right of the artist rendering below.


What is important is that these are difficult obstacles to overcome. They significantly slow down the movement of frozen material towards the central zone. Therefore, if more water is in the central area of ​​compact discs that with extended disks a very strong argument assert that it comes directly from the peripheral zone.

This is exactly what MIRI, the Webb Infrared Spectrometer, observed. The data confirmed that there is indeed an excess of water in the central region of the smaller, denser discs, where the ice floats freely without falling into a pressure trap. More broadly, this strongly suggests that indeed these frozen rocks serve as the starting point for rocky planets, as theory suggests.

A clue to the origin of the Earth

And for researchers, the conclusion is therefore crystal clear – it is true; this is the most convincing demonstration yet that Rocky planets like Earth were just small pebbles covered in ice early in their history.

Webb finally discovered the connection between the water vapor in the inner disk and the frozen rocks in the outer disk “, says Andrea Banzatti, an astrophysicist at Texas State University and lead author of the study.

In the past, we had a very static picture of planet formation, as if there were isolated regions from which planets emerged. », specifies his colleague Colette Salyk. ” We now have evidence that these areas interact “.

Incidentally, this work also testifies to Fr the incredible versatility of the James Webb telescope instruments. Although he specializes in the hunt for the origin of the universethrough the study of the objects that are located more than 13 billion light years awayit can also bring us information that directly concerns the history of our good old blue planet.

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