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To understand the origin of the diversity observed in exoplanetary systems,it is crucial to characterize the early stages of their formation, representedby Solar-type protostars. Likely, the gaseous chemical content of these objectsdirectly depends on the composition of the dust grain mantles formed before thecollapse. Directly retrieving the ice mantle composition is challenging, but itcan be done indirectly by observing the major components, such as NH3 and CH3OHat cm wavelengths, once they are released into the gas-phase during the warmprotostellar stage. We observed several CH3OH and NH3 lines toward three Class0 protostars in NGC1333 (IRAS 4A1, IRAS 4A2, and IRAS 4B), at high angularresolution (1"; ~300 au) with the VLA interferometer at 24-26 GHz. Using anon-LTE LVG analysis, we derived a similar NH3/CH3OH abundance ratio in thethree protostars (<0.5, 0.015-0.5, and 0.003-0.3 for IRAS 4A1, 4A2, and 4B,respectively). Hence, we infer they were born from pre-collapse material withsimilar physical conditions. Comparing the observed abundance ratios withastrochemical model predictions, we constrained the dust temperature at thetime of the mantle formation to be ~17 K, which coincides with the averagetemperature of the southern NGC 1333 diffuse cloud. We suggest that a brutalevent started the collapse that eventually formed IRAS 4A1, 4A2 and 4B,which,therefore, did not experience the usual pre-stellar core phase. Thisevent could be the clash of a bubble with NGC 1333 south, that has previouslybeen evoked in the literature.

Tracking the ice mantle history in the Solar-type Protostars of NGC 1333 IRAS 4