Earth has an enormous amount of water, but it is not even the most water-rich object in the Solar System (that honor belongs to Saturn’s moon Titan). Until the Moon it is richer in water than we thought. The question is, how did all that water end up in the solar system? Analysis of the asteroid samples broughtdays by the Hayabusa probe offers an interesting explanation.
The mission Hayabusa, developed jointly between NASA and the Japanese Space Agency, was not only the first to land on an asteroid. It was also the first to bring samples of that asteroid back to Earth (25143 Itokawa) back to our planet. Those samples arrived in 2016, and since then they have been the subject of different studies. The last of those studies has just been published in Nature Astronomy, and it has to do with water.
What the study authors have discovered is that the dust and rocks that make up the asteroid 25143 Itokawa are much richer in water than previously thought. By extrapolating what we know about the sample, the researchers estimate that in each cubic meter of regolith and rocks that make up the asteroid there are no less than 20 liters of water.
Not only that, the chemical analysis of that water is consistent with an idea that we were already considering when studying the lunar regolith, that the origin of that water is none other than the Sun, or more specifically, the solar wind. The hypothesis is that lThe protons from the solar wind bombard objects without an atmosphere such as the Moon and asteroids, interacting with the silicate molecules present in the regolith and forming water. Later, that water ends up falling on different planets.
In fact, the formation of this water by bombardment of solar radiation implies that the smallest objects such as dust are the ones that accumulate more water depending on their volume. Every year it is estimated that they fall 30,000 tons of space dust on earth. It is not much, but if we extend that bombardment over billions of years it is very possible that the water from that dust and small rocks will end up forming huge oceans. The same oceans that we enjoy here on Earth. Even the isotopic composition of terrestrial water (lighter than that of the minerals that make up our planet) fits that idea. In the end, everything is made of stars directly or indirectly. To the sea. [Nature Astronomy vía Ars Technica]