## 3 Results  
Our initial strategy was to detect ribonucleoside degradation products, formed in the solid state using a ceramic mortar and a pestle (see Section 2). From this, a very low single crystal was obtained upon crystallization, revealing the structure Guanine2-Mg(6H\({}_{2}\)O) (Figure 11, Table 11). Manual grinding experiments led to the formation of the already disclosed monohydrate hydrochloride guanine (Figure 12), which was included in a very recent paper as the main degradation product of an acidic solution of guanosine with magnesium carbonate [33]. Subsequently, all canonical ribonucleosides were tested with different salts (K\({}_{2}\)CO\({}_{3}\), Na\({}_{2}\)CO\({}_{3}\), CaCO\({}_{3}\), MgCO\({}_{3}\), and ZnCO\({}_{3}\)) under several conditions. From these experiments, the same hydrochloride guanine crystal structure was obtained (Figure 12) as previously reported GUANCD structures at CSD [34]. This structure is extensively described in the literature under acidic conditions [35]. This degradation was most likely induced by acid-catalyzed hydrolysis rather than exclusively by mechanochemical-induced degradation [12].  
Nevertheless, mechanochemical energy using a ball mill was thought to induce ribonucleoside degradation, as previously demonstrated for guanosine and uridine [25]. In the present work, the mechanochemical experiments using a ball mill were applied for all canonical ribonucleosides with different metal (present in extraterrestrial samples) salts and sodium carbonate. The degradation samples of purine (Figure 1, guanosine and adenosine) and pyrimidine (Figure 2, cytidine and uridine) ribonucleosides were recovered and analyzed in HPLC-UV.  
From purine ribonucleoside samples (Figure 1), the presence of the nucleobase is evident with all the tested salts (nickel chloride, NiCl\({}_{2}\).6H\({}_{2}\)O, aluminum chloride, AlCl\({}_{3}\).6H\({}_{2}\)O, iron sulfate, FeSO\({}_{4}\).7H\({}_{2}\)O) except for sodium carbonate, Na\({}_{2}\)CO\({}_{3}\). The brownish colors of the treated samples reveal purine ribonucleoside degradation (Figures 13 and 14). Of all the salts, aluminum chloride was the most reactive (Figure 1, G.2.1 to G.2.4 and A.2.1 to A.2.4). Iron species only reacted by pre-heating the ribonucleoside-metal mixture before mechanochemistry. Samples containing nickel chloride and without pre-heating could not be processed in the mechanochemical treatment (the sample became \"sticky\", caused by excessive water). Therefore, the mixtures were dried by heating (i.e., pre-heating procedure) before mechanochemistry treatment.  
Figure 1: Degradation of purine Ribonucleosides guanosine **(left)** and adenosine (**right**) into corresponding nucleobases (guanine and adenine, respectively) with different salts and conditions. The ball mill frequency was the equipment’s maximum frequency of 29.5 Hz. G—guanosine; g—guanine; A—adenosine; a—adenine; r.t—room temperature; p.t—pre-heating treatment;?—unknown species.  
Figure 2: Degradation of purine ribonucleosides cytidine **(left)** and uridine (**right**) into corresponding nucleobases (cytosine and uracil, respectively) with different salts and conditions. The ball mill frequency was the equipment’s maximum frequency of 29.5 Hz. C—cytidine; c—cytosine; U—uridine; u—uracil; r.t—room temperature; p.t—pre-heating treatment;?—unknown species.  
Looking up to pyrimidine ribonucleucosides (Figure 2) and analogs to purines, the presence of nucleobase is evident in samples with nickel chloride, aluminum chloride, and iron sulfate (C.1.1, C.2.1 to C.2.4 and C.3.1 to C.3.2; U.1.1, U.2.1 to U.2.4 and U.3.1 to U.3.2). The brownish colors of some samples (Figures A5 and A6) demonstrate pyrimidine ribonucleoside degradation. Reaction with iron sulfate was promoted when the pre-heating procedure was applied before mechanochemistry. Similarly to purine ribonucleosides, nickel chloride samples could not be obtained without the pre-heating treatment.