(ORDO NEWS) — In a new study, Mark Elowitz and his colleagues present the first analysis of far-ultraviolet reflectance spectra captured for regions located on different hemispheres of Saturn’s moon Rhea – the slave and the master.
These spectra were recorded using the UV spectrograph of the Cassini spacecraft (“Cassini”) during flights past this moon of Saturn. In this work, the researchers set out to explain the origin of an unidentified broad spectral line, the center of which is located near the 184 nanometer mark. Using laboratory measurements of the parameters of UV spectra for a whole set of molecules, Elowitz and his colleagues found a good agreement with the spectra of a substance from the surface of Rhea – hydrazine monohydrate molecules or several chlorine-containing molecules.
In the work, the researchers showed that hydrazine monohydrate is the most likely candidate to explain the absorption line at 184 nanometers. Hydrazine also served as a working fluid in the thrusters of the Cassini spacecraft, but this time the probe did not use these engines when flying past Rhea, so the observed signal could not be attributed to the spacecraft’s fuel. The scientists then showed in the study a possible mechanism for the formation of hydrazine on ice surfaces.
To explain the origin of hydrazine, Elowitz and his team proposed a mechanism involving reactions between water ice and ammonia, or the delivery of hydrazine from Titan’s nitrogen-rich atmosphere. Irradiation of ammonia by charged particles from Saturn’s magnetosphere caused the dissociation of ammonia molecules and the formation of diazene and hydrazine.
The source of ammonia on Rhea could have been of primary origin, be located in the bowels of the satellite during its formation and rise to the surface during the period of endogenous activity, as evidenced by images obtained with the Cassini apparatus, although the prolonged presence of ammonia on the surface seems unlikely, the authors found out.
Elowitz’s team sees a deeper analysis of the spectra to assess the possibility of transfer of matter from Titan’s atmosphere to Rhea’s atmosphere as a direction for their further research, which may help explain the presence of hydrazine monohydrate on this moon of Saturn.
The research is published in the journal Science Advances.
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