  Interplanetary dust particles (IDPs) were likely major sources of
extraterrestrial organics to the early Earth. However, IDPs experience heating
to > 500 ${\deg}$C for up to several seconds during atmospheric entry. In this
study, we aim to understand the effects of atmospheric entry heating on the
dominant organic component in IDPs by conducting flash heating experiments (4 s
to 400 {\deg}C, 600 {\deg}C, 800 {\deg}C, and 1000 {\deg}C) on insoluble
organic matter (IOM) extracted from the meteorite Cold Bokkeveld (CM2). For
each of the experimental charges, the bulk isotopic compositions of H, N, and C
were analyzed using IRMS, the H isotopic heterogeneities (occurrence of
hotspots) of the samples were measured by NanoSIMS, and the functional group
chemistry and ordering of the IOM was evaluated using FTIR and Raman
spectroscopy, respectively. IOM in particles heated to > 600 {\deg}C
experienced loss of isotopically heavy, labile H and N groups, resulting in
decreases in bulk ${\delta}$D, ${\delta}$15N, H/C and, upon heating > 800
{\deg}C, in N/C. The H heterogeneity was not greatly affected by flash heating
to < 600 {\deg}C, although the hotspots tended to be less isotopically
anomalous in the 600 {\deg}C sample than in the 400 {\deg}C sample. However,
the hotspots all but disappeared in the 800 {\deg}C sample. Loss of C=O groups
occurred at 800 {\deg}C. Based on the Raman G-band characteristics, the heating
resulted in increased ordering of the polyaromatic component of the IOM. The
data presented in this study show that all aspects of the composition of IOM in
IDPs are affected by atmospheric entry heating. Modelling and temperature
estimates from stepwise release of He has shown that most IDPs are heated to >
500{\deg}C (Love and Brownlee, 1991; Nier and Schlutter, 1993), hence,
atmospheric entry heating is expected to have altered the organic matter in
most IDPs.
