Newborn stars usually go through a juvenile stage where the intense radiation they emit washes away the gaseous environment in which they formed through the gravitational collapse of a nebula. As the nebular gas dissipates, the temperature around the star drops enough to allow tiny minerals, ice and organic matter to condense. These materials collide and form aggregates that accumulate around young stars, forming what are called protoplanetary disks.
These massive structures, originally formed from tiny particles of dust and gas surrounding young stars, have evolved into kilometer-long bodies such as asteroids and comets. From collisions between these early solid bodies, on longer time scales, rocky planets like Earth would later emerge.
Our concern now is to explore, with the revolutionary James Webb Space Telescope, how water travels in these primary planetary systems.
Freezing water from the ends
In general, there are two types of protoplanetary disks, the so-called compact and the extended. The JWST space telescope recently revealed the transport processes of water and volatiles within protoplanetary disks.
Specifically, the paper published today presents JWST-MIRI spectra of four selected protoplanetary disks, two of each type, to test whether water vapor within the ice line is controlled by the drift of solid materials that form. inside.
In those albums they were very dynamic. Small solid rocks are actually aggregates of small micrometric minerals, ice and organic matter that have collided with each other. They form porous aggregates that can easily incorporate ice.
In the cold regions outside the disk, water tends to condense and form ice sheets on these small rocks. The presence of these frozen mantles means that the particles are able to disperse better in a medium with high water vapor, as is the case inside compact discs, unlike discs where this vapor is scarce.
Water on Earth from a very early age
This is key because the Earth was formed near the Sun in a hot environment and, therefore, with a relative scarcity of water. However, this mechanism must have worked for a long time to hydrate the formative region of our planet and ensure that the Earth had water from an early age.
The reason for these differences in protoplanetary disks is explained in an elegant and simple way: the capricious channels of water aboard the materials that form these disks.
Water watchers reveal their secrets
The very large resolving power of the mid-infrared spectrometer (MIRI) allows obtaining very detailed water spectra. This reveals the excess emission of spectral lines in the materials that make up compact discs compared to extended discs. This excessive emission indicates that there is a cold component that extends far from these stars, between one and ten times that separates the Earth from the Sun in our planetary system.
The outflow of cold water is due to the sublimation of ice and the diffusion of water vapor through the disk. This means that these rocky and ice-covered aggregates move more efficiently toward regions close to the star when there is enough water vapor, something that happens in compact disks.
Pebbles play a fundamental role: they are responsible for transporting large amounts of water and other volatiles to the internal regions of the disk where the embryos of rocky planets are formed.
As these materials decay toward the star, they tend to accumulate and form the toroidal rings and voids that are common in extended protoplanetary disks. The early formation of gas giant planets, such as Jupiter itself, may have played a fundamental role in acting as a barrier to the passage of these materials into more internal regions.
Who would have believed that, thanks to the flexible and intricate paths followed by water on small stones, today the Earth has a liquid element, which can make it a world of oceans and an oasis of life.
Josep M. Trigo Rodríguez, Principal Investigator of the Meteorite, Minor Bodies and Planetary Sciences Group, Institute of Space Sciences (ICE – CSIC)
