2002ApJ...576..255L

We present Berkeley-Maryland-Illlinois Association array observations of formic acid (HCOOH) at 1 mm toward the Orion KL region. Near the compact ridge, HCOOH emission is spatially resolved; its partial shell morphology is different from that of other complex O-bearing molecules such as methyl formate and dimethyl ether. This unique distribution suggests that HCOOH is located in a layer that delineates the interaction region between the outflow and the ambient quiescent gas. HCOOH is also detected toward the hot core. For both cases, ejection of grain mantles is likely to be responsible for the observed HCOOH.