EDP Sciences
Free access
Volume 433, Number 2, April II 2005
Page(s) 583 - 590
Section Interstellar and circumstellar matter
DOI http://dx.doi.org/10.1051/0004-6361:20042443

A&A 433, 583-590 (2005)
DOI: 10.1051/0004-6361:20042443

Formation and photostability of N-heterocycles in space

I. The effect of nitrogen on the photostability of small aromatic molecules
Z. Peeters1, O. Botta1, 2, S. B. Charnley3, Z. Kisiel4, Y.-J. Kuan5, 6 and P. Ehrenfreund1

1  Astrobiology Laboratory, Leiden Institute of Chemistry, PO Box 9502, 2300 RA Leiden, The Netherlands
    e-mail: peeters@strw.leidenuniv.nl
2  International Space Science Institute, Hallerstrasse 6, 3012 Bern, Switzerland
3  Space Science Division, NASA Ames Research Center, MS 245-3, Moffett Field, CA 94035, USA
4  Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw, Poland
5  Department of Earth Sciences, National Taiwan Normal University, 88 Sec. 4 Ting-Chou Road, Taipei 116, Taiwan
6  Institute of Astronomy and Astrophysics, Academia Sinica, PO box 23-141, Taipei 106, Taiwan

(Received 26 November 2004 / Accepted 14 December 2004)

Nitrogen-containing cyclic organic molecules (N-heterocycles) play important roles in terrestrial biology, for example as the nucleobases in genetic material. It has previously been shown that nucleobases are unlikely to form and survive in interstellar and circumstellar environments. Also, they were found to be unstable against ultraviolet (UV) radiation. However, nucleobases were detected in carbonaceous meteorites, suggesting their formation and survival is possible outside the Earth. In this study, the nucleobase precursor pyrimidine and the related N-heterocycles pyridine and s-triazine were tested for UV stability. All three N-heterocycles were found to photolyse rapidly and their stability decreased with an increasing number of nitrogen atoms in the ring. The laboratory results were extrapolated to astronomically relevant environments. In the diffuse interstellar medium (ISM) these N-heterocycles in the gas phase would be destroyed in 10-100 years, while in the Solar System at 1 AU distance from the Sun their lifetime would not extend beyond several hours. The only environment where small N-heterocycles could survive, is in dense clouds. Pyridine and pyrimidine, but not s-triazine, could survive the average lifetime of such a cloud. The regions of circumstellar envelopes where dust attenuates the UV flux, may provide a source for the detection of N-heterocycles. We conclude that these results have important consequences for the detectability of N-heterocycles in astronomical environments.

Key words: astrobiology -- methods: laboratory -- stars: individual: CRL 618

SIMBAD Objects

© ESO 2005

What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access.

An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.

  • If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
  • You can define your own OpenURL resolver with your EDPS Account.
    In this case your choice will be given priority over that of your library.
  • You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.