Cosmic carbon chemistry: from the interstellar medium to the early Earth

Abstract

Astronomical observations have shown that carbonaceous compounds in the gas and solid state, refractory and icy are ubiquitous in our and distant galaxies. Interstellar molecular clouds and circumstellar envelopes are factories of complex molecular synthesis. A surprisingly large number of molecules that are used in contemporary biochemistry on Earth are found in the interstellar medium, planetary atmospheres and surfaces, comets, asteroids and meteorites, and interplanetary dust particles. In this article we review the current knowledge of abundant organic material in different space environments and investigate the connection between presolar and solar system material, based on observations of interstellar dust and gas, cometary volatiles, simulation experiments, and the analysis of extraterrestrial matter. Current challenges in astrochemistry are discussed and future research directions are proposed.

Figure 1.

Carbon pathways between interstellar and circumstellar regions and the forming solar system.

Figure 2.

Astronomical spectra of the infrared vibrational modes (at 3.3, 6.2, 7.7, 8.6, 11.2, and 12.7 µm) of PAH molecules in three objects that represent the different peak positions and relative intensities observed in various galactic and extragalactic regions (see Peeters et al. 2002). Classes A, B and C represent the three different astronomical environments; (A) ISM, reflection nebulae, HII regions; (B) a few post-AGB and Herbig Ae/Be stars and most Planetary Nebulae; (C) a few peculiar post-AGB stars.

Figure 3.

A few examples of PAH structures that might be present in the ISM.

Figure 4.

The gas chromatography/mass spectrometer spectrum for the peak assigned to BSTFA (N,o-Bis Trimethylsilyl (trifluoroacetamide) derivatization reagent) derivatized uracil and its structure. The inset shows the mass spectrum of a BSTFA-derivatized uracil standard (Martins et al. 2008).