Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Racemic amino acids from the ultraviolet photolysis of interstellar ice analogues


The delivery of extraterrestrial organic molecules to Earth by meteorites may have been important for the origin and early evolution of life1. Indigenous amino acids have been found in meteorites2—over 70 in the Murchison meteorite alone3. Although it has been generally accepted that the meteoritic amino acids formed in liquid water4 on a parent body, the water in the Murchison meteorite is depleted in deuterium5 relative to the indigenous organic acids6,7. Moreover, the meteoritical evidence8 for an excess of laevo-rotatory amino acids is hard to understand in the context of liquid-water reactions on meteorite parent bodies. Here we report a laboratory demonstration that glycine, alanine and serine naturally form from ultraviolet photolysis of the analogues of icy interstellar grains. Such amino acids would naturally have a deuterium excess similar to that seen in interstellar molecular clouds, and the formation process could also result in enantiomeric excesses if the incident radiation is circularly polarized. These results suggest that at least some meteoritic amino acids are the result of interstellar photochemistry, rather than formation in liquid water on an early Solar System body.

This is a preview of subscription content, access via your institution

Relevant articles

Open Access articles citing this article.

Access options

Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: Amino acids are formed by the UV photolysis of a realistic interstellar ice analogue.


  1. Oró, J. Comets and the formation of biochemical compounds on the primitive Earth. Nature 190, 389–390 (1961).

    Article  ADS  Google Scholar 

  2. Cronin, J. R. & Pizzarello, S. Amino acids in meteorites. Adv. Space Res. 3, 5–18 (1983).

    Article  CAS  Google Scholar 

  3. Cronin, J. R. & Chang, S. in Chemistry of Life's Origins (NATO ASI) (eds Greenberg, J. M., Pirronello, V. & Mendoza-Gomez, C.) 209–258 (Kluwer, Dordrecht, 1993).

    Book  Google Scholar 

  4. Peltzer, E. T., Bada, J. L., Schlesinger, G. & Miller, S. L. The chemical conditions on the parent body of the Murchison meteorite: Some conclusions based on amino, hydroxy nd dicarboxylic acids. Adv. Space. Res. 4, 69–74 (1984).

    Article  ADS  CAS  Google Scholar 

  5. Robert, F. & Epstein, S. The concentration and isotopic composition of hydrogen, carbon and nitrogen in carbonaceous meteorites. Geochim. Cosmochim. Acta 46, 81–95 (1982).

    Article  ADS  CAS  Google Scholar 

  6. Lerner, N. R. Influence of Murchison or Allende minerals on hydrogen-dueterium exchange of amino acids. Geochim. Cosmochim. Acta 59, 1623–1631 (1995).

    Article  ADS  CAS  Google Scholar 

  7. Lerner, N. R. Influence of Allende minerals on deuterium retention of products of the Strecker synthesis. Geochim. Cosmochim. Acta 61, 4885–4893 (1997).

    Article  ADS  CAS  Google Scholar 

  8. Cronin, J. R. & Pizzarello, S. Enantiomeric excesses in meteoritic amino acids. Science 275, 951–955 (1997).

    Article  ADS  CAS  Google Scholar 

  9. Sandford, S. A. The inventory of interstellar materials available for the formation of the Solar System. Meteorit. Planet. Sci. 31, 449–476 (1996).

    Article  ADS  CAS  Google Scholar 

  10. Gibb, E. L. et al. An inventory of interstellar ices toward the embedded protostar W33A. Astrophys. J. 536, 347–356 (2000).

    Article  ADS  Google Scholar 

  11. Gerakines, P. A., Schutte, W. A. & Ehrenfreund, P. Ultraviolet processing of interstellar ice analogs. I. Pure ices. Astron. Astrophys. 312, 289–305 (1996).

    ADS  CAS  Google Scholar 

  12. Tegler, S. C. et al. Detection of the 2165 inverse centimeter (4.619 micron) XCN band in the spectrum of L1551 IRS 5. Astrophys. J. 411, 260–265 (1993).

    Article  ADS  CAS  Google Scholar 

  13. Bernstein, M. P., Sandford, S. A., Allamandola, L. J., Chang, S. & Scharberg, M. A. Organic compounds produced by photolysis of realistic interstellar and cometary ice analogs containing methanol. Astrophys. J. 454, 327–344 (1995).

    Article  ADS  CAS  Google Scholar 

  14. Kerridge, J. F. Formation and processing of organics in the early Solar System. Space Sci. Rev. 90, 275–288 (1999).

    Article  ADS  CAS  Google Scholar 

  15. Teixeira, T. C., Devlin, J. P., Buch, V. & Emerson, J. P. Discovery of solid HDO in grain mantles. Astron. Astrophys. 347, L19–L22 (1999).

    ADS  CAS  Google Scholar 

  16. Turner, B. E. Deuterated molecules in translucent and dark clouds. Astrophys. J. Suppl. Ser. 136, 579–629 (2001).

    Article  ADS  CAS  Google Scholar 

  17. Lacy, J. H., Faraji, H., Sandford, S. A. & Allamandola, L. J. Unravelling the 10 µm ‘Silicate’ feature of protostars: the detection of frozen interstellar ammonia. Astrophys. J. 501, L105–L109 (1998).

    Article  ADS  CAS  Google Scholar 

  18. Chiar, J. E. et al. The composition and distribution of dust along the line of sight towards the Galactic center. Astrophys. J. 537, 749–762 (2000).

    Article  ADS  CAS  Google Scholar 

  19. Allamandola, L. J., Sandford, S. A., Tielens, A. G. G. M. & Herbst, T. M. Spectroscopy of dense clouds in the C-H stretching region: methanol and “diamonds”. Astrophys. J. 399, 134–146 (1992).

    Article  ADS  CAS  Google Scholar 

  20. Irvine, W. M. Spectroscopic evidence for interstellar ices in Comet Hyakutake. Nature 383, 418–420 (1996).

    Article  ADS  CAS  Google Scholar 

  21. Allamandola, L. J., Sandford, S. A. & Valero, G. Photochemical and thermal evolution of interstellar/pre-cometary ice analogs. Icarus 76, 225–252 (1988).

    Article  ADS  CAS  Google Scholar 

  22. Matthews, C. N. & Moser, R. E. Peptide synthesis from hydrogen cyanide and water. Nature 215, 1230–1234 (1967).

    Article  ADS  CAS  Google Scholar 

  23. Ehrenfreund, P., Bernstein, M. P., Dworkin, J. P., Sandford, S. A. & Allamandola, L. J. The photostability of amino acids in space. Astrophys. J. 550, L95–L99 (2001).

    Article  ADS  CAS  Google Scholar 

  24. Sorrell, W. H. Origin of amino acids and organic sugars in interstellar clouds. Astrophys. J. 555, L129–L132 (2001).

    Article  ADS  CAS  Google Scholar 

  25. Rubenstein, E., Bonner, W. A., Brown, G. S. & Bailey, J. Polarized stellar light. Science 283, 1415 (1999).

    Article  ADS  Google Scholar 

  26. Rubenstein, E., Bonner, W. A., Noyes, H. P. & Brown, G. S. Supernovae and life. Nature 306, 118 (1983).

    Article  ADS  Google Scholar 

  27. Bonner, W. A. & Bean, B. D. Asymmetric photolysis with elliptically polarized light. Orig. Life Evol. Biosphere 30, 513–517 (2000).

    Article  ADS  CAS  Google Scholar 

  28. Warneck, P. A microwave-powered hydrogen lamp for vacuum ultraviolet photochemical research. Appl. Opt. 1, 721–726 (1962).

    Article  ADS  CAS  Google Scholar 

  29. Prasad, S. S. & Tarafdar, S. P. UV radiation field inside dense clouds—Its possible existence and chemical implications. Astrophys. J. 267, 603–609 (1983).

    Article  ADS  CAS  Google Scholar 

  30. Zhao, M. & Bada, J. L. Determination of alpha-dialkylamino acids and their enantiomers in geological samples by high-performance liquid chromatography after derivatization with a chiral adduct of o-phthaldialdehyde. J. Chromatogr. A 690, 55–63 (1995).

    Article  CAS  Google Scholar 

Download references


This work was supported by NASA grants from the Origins of Solar Systems, Exobiology, and Astrobiology programmes, as well as the NASA Ames Director's Discretionary Fund. We thank A. Weber, D. Glavin, O. Botta, J. Chambers and K. Nelson for discussions. We also acknowledge technical support from R. Walker.

Author information

Authors and Affiliations


Corresponding author

Correspondence to Max P. Bernstein.

Ethics declarations

Competing interests

The authors declare that they have no competing financial interests

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Bernstein, M., Dworkin, J., Sandford, S. et al. Racemic amino acids from the ultraviolet photolysis of interstellar ice analogues. Nature 416, 401–403 (2002).

Download citation

  • Received:

  • Accepted:

  • Issue Date:

  • DOI:

This article is cited by


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing