Scientific quality of the proposal
The origin and evolution of the molecular universe starts
with the injection of material - much of it in molecular or
solid form - by stars in the later stages of their evolution,
the processing of this material in the interstellar medium by
the prevalent ultraviolet radiation fields, energetic
particles, and strong shocks, and ends with the
incorporation of this material into newly formed stars and
their budding planetary systems. In this way, the chemical
processes taking place in the interstellar medium may
eventually be inherited by planetary systems. Charting this
prebiotic evolution and its relationship to the origin of
life on earth and possibly other planetary systems in the
universe is a key problem within astrophysics.
While the first observations of molecules date back to the
earliest parts of the last century, only over the last
decade, it has become clear that we actually live in a
molecular universe. A variety of observations have shown that
surprisingly complex molecules are an important component of
the interstellar medium. These include the vibrational
signatures of large Polycyclic Aromatic Hydrocarbon molecules
(PAHs) which dominate the mid-infrared spectra of
galaxies as a whole as well as many objects therein, the
electronic fingerprints of a variety of complex molecules
(carbon chains, fullerenes, and PAHs) in the form of diffuse
absorption bands in the visible spectra of stars, and the
rotational transitions of some 150 smaller molecules such as
ammonia and water in the microwave spectral range.
Molecules have an important influence on the
heating and cooling of interstellar gas and, therefore, on the
cloud structure of the interstellar medium in galaxies.
Molecular clouds are
the (only) site of ongoing star formation to a large extent
because molecules are efficient gas coolers, thereby
diminishing thermal support relative to self-gravity.
Moreover, molecules suppress the degree of ionization in
these clouds and therefore ``decouple'' the gas from any
supporting magnetic fields. Molecules play, thus, a key role
in the process of star formation.
Hence, molecules are directly interwoven into the fabric of
the universe. They are an important component of the universe
and play a central role in many key processes that dominate
the structure and evolution of galaxies. Understanding the
origin and evolution of interstellar molecules is therefore a
fundamental goal of modern astrophysics.