As you know, asteroids are debris left behind by larger bodies that were shattered by a large impact event. According to Dr. Ralph Milliken, a planetary scientist at Brown University who co-authored a study on Ryugu, the latter is a conglomerate of loose rocks held together by gravity. Nothing less than a pile of rubble wandering around in space.
On Ryugu, scientists have detected a water signature. And according to them, this water comes from a previously richer asteroid relative in water that has probably dried out . However, it would also be possible that Ryugu had dried out after a catastrophic disturbance, or that it warmed up after a few close turns to the Sun in the past, which would have dried up its surface.
In order to determine which scenario would be the most likely, observations of the Ryugu underground samples were made, coupled with observations by the near infrared spectrometer (NIRS3) of JAXA's Hayabusa-2 probe.
And scans ultimately reveal that Rygu's former parent body had dried out during some sort of event that heated him up before he was born.
What we learn from the samples from the Hayabusa-2 mission
As a reminder, an artificial impact experiment on Ryugu was carried out by the Haybusa-2 mission in April 2019. It consisted of collecting and studying the underground materials exposed in order to learn more about the object.
The mission's experts thus used the near infrared spectrometer (NIRS3) to detect aquifer minerals in order to be able to compare the water content of the surface rock with that of the subsoil.
Analyzes of the data revealed that the signature of the groundwater was quite similar to that of the outermost surface. These results therefore agree with the hypothesis that Ryugu's parent body had already dried up , unlike the other theory arguing that Ryugu's surface was dried up by the Sun.
Dr Milliken also stressed that one should not expect that the high temperature heating of the Sun will only have effects on the surface of Ryugu, without penetrating far into its basement. And he adds: "But we can see that the surface and the subsoil have a similarity and both are relatively poor in water, which brings us back to the idea that Ryugu did come from the alteration of his body. parental ”.
The results of this study were published in the journal Nature Astronomy .