TITLE: Polyaromatic hydrocarbons in spectra of comets

AUTHOR: Alexey Berezhnoy, Sternberg Astronomical Institute, Moscow, Russia

ABSTRACT:
Presence of polyaromatic hydrocarbons (PAH) such as pyrene, anthracene, 
and phenanthrene in the comet Halley is discussed. Possibility of detection 
of luminescence continuum as a tracer of presence of PAHs in comets during 
Earth-based spectral observations of comets is studied.
Delivery of complex organic compounds to Mars and the Moon by impacts of
comets is considered. Complex organic compounds including PAHs can survive
during low-speed collisions of comets with planets. Fluorescence spectra
of pyrene are considered. Identification of vibronic bands of pyrene in
cometary spectra on the basis of its spectra in organic solvents is
inadequate, while frozen matrices represent a better model. Based on
fluorescence spectra, it is possible also to distinguish gas-phase pyrene
and pyrene in water ice matrices. Additional observations of comets are
required for checking of possible presence of luminescent continuum in
optical spectra of comets.