  To understand the origin of the diversity observed in exoplanetary systems,
it is crucial to characterize the early stages of their formation, represented
by Solar-type protostars. Likely, the gaseous chemical content of these objects
directly depends on the composition of the dust grain mantles formed before the
collapse. Directly retrieving the ice mantle composition is challenging, but it
can be done indirectly by observing the major components, such as NH3 and CH3OH
at cm wavelengths, once they are released into the gas-phase during the warm
protostellar stage. We observed several CH3OH and NH3 lines toward three Class
0 protostars in NGC1333 (IRAS 4A1, IRAS 4A2, and IRAS 4B), at high angular
resolution (1"; ~300 au) with the VLA interferometer at 24-26 GHz. Using a
non-LTE LVG analysis, we derived a similar NH3/CH3OH abundance ratio in the
three 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 with
similar physical conditions. Comparing the observed abundance ratios with
astrochemical model predictions, we constrained the dust temperature at the
time of the mantle formation to be ~17 K, which coincides with the average
temperature of the southern NGC 1333 diffuse cloud. We suggest that a brutal
event started the collapse that eventually formed IRAS 4A1, 4A2 and 4B,
which,therefore, did not experience the usual pre-stellar core phase. This
event could be the clash of a bubble with NGC 1333 south, that has previously
been evoked in the literature.
