1 Science (1999) Vol. 283 p

2 Introduction A Brief Introduction - Max How we know polycyclic aromatic hydrocarbons are ubiquitous and abundant in space - Lou Interstellar conditions and how we simulate them - Scott How we analyzed the samples (L2MS) - Dick Our results and their astrobiological significance - Max Conclusions - Max

3 A little context…  Space was considered chemically barren for most of the 20th Century  The spell was broken in the 1960’s and 1970’s with these discoveries: OH (early 60’s) NH 3 (1968) H 2 CO (1969)* CO (1970) 11.3 µm emission (1973) * …polyatomic molecules containing at least 2 atoms other than H can form in the interstellar medium.” Snyder, Buhl, Zuckerman, Palmer

4 Center of the Orion Nebula

5 EMISSION FROM ORION

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7 Soot Particles are Mainly PAHS SOOT PARTICLEPAH MOLECULE

8 Darken room and cover projector lens for fluorescence demonstration

9 UV UV Pumped Infrared Fluorescence

10 PAH EMISSION FROM NEARBY SPIRAL GALAXY MESSIER 81.

11 PAH EMISSION FROM THE SOMBRERO GALAXY MESSIER 104.

12 What happens to PAHS in Cold, Dark Interstellar Clouds ??? TOP OF THE HORSEHEAD NEBULA

13 Astrochemistry - A middling difficult enterprise “Physicists love the early universe -- because it is EASY. You’ve got protons, electrons, light, and that’s it. Once atoms come together, you get chemistry, then biology, then economics… it pretty much goes to hell.” -Andrew Lange (5/3/2000)

14 How do we simulate chemistry in the interstellar medium? Much of the material in galaxies exists in ‘Dense Molecular Clouds’ that consist of a mixture of dust, gas, and ices

15 How do we simulate the interstellar medium? These ‘dense’ clouds are the site of star formation Material from these clouds can find its way into/onto newly formed planets

16 The dust in these dense clouds blocks out starlight and their interiors can get very cold (T < 50 K). How do we simulate the interstellar medium? The pressures are very low

17 How do we simulate the interstellar medium? The radiation field can be high (UV and particle radiation) This radiation clearly illuminates PAHs associated with the clouds Visible LightPAH Emission

18 Bernstein, Sandford, Allamandola, Sci. Am. 7,1999, p26 Interstellar Dust: ice mantle evolution Thus, at the low temperatures found in these clouds, most molecules are expected to freeze out onto the dust grains where they may be exposed to ionizing radiation

19 We can get an idea of what the ices are made of by measuring the absorption spectra of the cloud material The main ice ingredient is always H 2 O.

20 So, to simulate dense cloud conditions we need to recreate low T, low P, high radiation conditions with PAHs in H 2 O-rich ices exposed to radiation Cryo-vacuum Sample Head

21 Lots of “plumbing”… Cryo-vacuum System (w/o spectrometer) H 2 Lamp On

22 Brown Organic Residue Produced by Low Temperature UV Ice Irradiation

23 Analysis of the Samples

24 Laser-Desorption Laser-Ionization Mass Spectrometer

25 Two-Step Laser Mass Spectrometry pulsed IR laser sample A A A B B B plume of neutral molecules to detector pulsed UV laser selective ionization of aromatics B B B A A A A+ I. Laser desorption of neutral molecules II. Laser ionization of selected species

26 Principles of Time-of-Flight Mass Spectrometry Kinetic Energy = z  V = 1 / 2 mv 2 Arrival Time = t = d/v = d/[(2z  V/m)] 1/2 = d[m/(2z  V)] 1/2

27 time of flight chamber pulsed IR beam pulsed UV beam Reflectron Mass Deflectors Einzel lens Acceleration grids MCP detector Two-Step Laser Mass Spectrometry

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29 The peaks at 316, 332, and 348 amu correspond to the addition of one to three O atoms, respectively, likely in the form of ketones or hydroxyl side groups (or both).

30 The peak at 290 amu corresponds to the addition of an O atom with loss of two H atoms, consistent with an ether bridging the molecule’s bay region.

31 Summary

32 Astrobiological Implications: The Search for Life and see a whale breaching in the oceans of Europa

33 Alkylated PAHs were invoked as biomarkers in the Martian meteorite ALH84001 McKay et al., (1996) Science, Vol. 273, p "Search for past life on Mars: Possible relic biogenic activity in martian meteorite ALH84001" Astrobiological Implications: The Search for Life

34 Astrobiological Implications: The Search for Life

35 Thermoproteus tenax (a "primitive" organism) use menaquinones as their primary quinone, and in most Bacteria and Archaea, MK and related naphthoquinones seem to be very fundamental = ancient: are manufactured via Shikimate, couple important biochemical reactions (i.e. Fumarate to Succinate), are involved in active transport of amino acids, and replace or augment ubiquinone or plastoquinone as electon transport and oxidative phosphorylation co-enzymes Astrobiological Implications: The Origin of Life We see this class of compounds facilitating the most basic chemical reactions in "primitive" organisms thus we believe that these molecules are ancient

36 Conclusions The results explain many molecules seen in meteorites. These species resemble biomarkers, and thus are relevant to the search for life. They are members of a class of compounds that is ubiquitous in space. Quinones play fundamental roles in life's chemistry now and probably did so from the beginning.

37 Thanks Advice, edits, and patience of our friends here at NASA-Ames and Stanford, Technical support from dedicated lab technicians, Support from our local management and, Financial support from NASA's Astrophysics and Planetary Science Divisions at NASA HQ Our thanks also to our coauthor colleagues who were unable to attend this presentation. It wouldn’t have happened without them.

38 Prof. Zare receiving H. Julian Allen Award from Simon P. Worden, Ph.D., BGen. (USAF, Ret.), who is the Director of the NASA Ames Research Center

39 Photo of all presenters: Simon P. Worden, Scott A. Sanford, Richard N. Zare, Max P. Berstein, and Louis J. Allamandola. Unfortunately, two other authors could not be present: J. Seb Gillette and Simon J. Clemett. (Photo by Dr. Jennifer Heldmann)

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