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2005 Annual Science Report

NASA Goddard Space Flight Center Reporting  |  JUL 2004 – JUN 2005

Laser Mass Spectrometry Technique Development for Analysis of Complex Organics in Cometary and Meteritic Materials

Project Summary

Theme 4 work at JHU/APL using laser time-of-flight mass spectrometry (TOF-MS) techniques continues in collaboration with the GCA team and external partners.

4 Institutions
3 Teams
0 Publications
0 Field Sites
Field Sites

Project Progress

Theme 4 work at JHU/APL using laser time-of-flight mass spectrometry (TOF-MS) techniques continues in collaboration with the GCA team and external partners. We seek to contribute to research on the following major questions within the GCA:

  • What are the fine scale morphology and composition of comet nuclei?
  • Do comets comprise an enabling inventory of complex pre-biotic organics?
  • How should we approach the characterization of this inventory?

Laser desorption (LD) methods are complementary to ongoing non-laser GCA work at GSFC; they sample distinct yet related sets of compounds from complex samples. Our work is also a link between analyses performed with similar facility instrumentation at other labs in that we can measure quantitatively the scientific consequences of miniaturization or other resource limitations. The specific objectives of the laboratory-based effort at APL are to:

  1. Examine organics in standards , cometary analogs , and meteorites with Laser Desorption Mass Spectrometry (LDMS);
  2. Develop an LDMS sensitivity-selectivity database for high mass, refractory organics in various matrices and optimize the method;
  3. Compare LD-based “prompt ionization” with LD + laser post-ionization (REMPI) for use as organic chemical mapping technique; and
  4. Determine optimal combined LDMS and pyrolysis GCMS (and other) analyses of common samples which advise mission design .

We have continued to work with miniature LDMS prototypes, most recently with a “flight-scale” breadboard completed with separate NASA instrument support. To optimize this breadboard for the sample analyses we are conducting, we have improved the configuration as follows:

  1. Integration into new highly compact, vertical vacuum system ( Figure 1 ). Metallic seals are used to achieve lower base pressures for higher signal-to-noise for trace high-mass organics. The sample chamber has viewports to permit lateral incidence post-ionization.
  2. Development of a miniature xyz sample motion stage with lateral motion precisions of less than 10 ?m and x or y travel of 12.5 mm permits larger samples to be examined without having to break vacuum. This is valuable because organics related to inclusions in meteorites can be several mm across and/or separated by several mm. The process of breaking vacuum takes time and can change sensitivity/instrument bias.
  3. Sample-holding components and application techniques were further developed for a variety of minimally “prepared” materials (not dissolved, extracted, concentrated, etc.). For example, tailored surfaces such as etched silicon or otherwise treated wafer layers at sample deposit locations can entrap particles without adhesives. Results suggest that the deliberate localization of sample particles improves the mass resolution and signal to noise ratios because ions are emitted with sub-laser spot size initial spatial dispersion.

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A number of analyses have been conducted to understand further the sensitivities of various laser TOF-MS approaches to detection of high mass organics in neat samples, and to compare those with parallel studies at GSFC with GCMS, LCMS, and other techniques. Particularly in support of the LDMS organics database, we have begun to (i) reexamine earlier spectra from carbonaceous meteorites; (ii) analyze systematically a sequence of both procedural blanks and standard reference materials; and (iii) record new spectra from geo-standard and meteorite samples under identical conditions as the blanks and references.

In earlier analyses of the Allende CV3 meteorite, a number of complex organics including PAHs and alkylated PAHs were detected consistent with known instrument sensitivities. Higher mass compounds are primarily aromatic structures broken off the macromolecular network. A closer examination of the high-mass (m/z > 300 Da) signal revealed some similarities with and differences from LDMS and other observations of known macromolecular IOM in C-chondrite acid residues (Becker et al. 1997, Kissin et al. 2003). We observe a sequence of sodiated and potassiated parent compounds ( Table 1 ) with major adduct steps at ?m/z = 28 Da (dimethyl, C2H4, CH2N, etc.). A parent PAH at 428 Da (octacene or equivalent) may be one of the important higher-mass “building blocks” of more aromatic macromolecular IOM. However, prompt LDMS PAH ratios do not match those in REMPI (Plows et al. 2003, Elsila et al., 2004). Furthermore, fragmentation and cationization patterns with 355 nm LDMS are different than with 337 nm wavelength. These differences are attributable to both wavelength and mineral matrix (absorptivity) effects. Preliminary analysis of the CM2/CM1 chondrite ALH83100 revealed more extensive alkylation in this meteorite, with distinct reproducible peaks at somewhat ambiguous m/z values of 116, 158, 196, and 412. Additional extensive comparative analyses of ALH83100, Murchison, and Allende are planned.

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Two new staff members are participating in the GCA research effort. Catherine Corrigan (Postdoctoral Associate) joined JHU/APL from the Smithsonian NMNH where she worked with Tim McCoy and others on meteorite research. Anita Ganesan (Astrobiology Research Associate), who joined JHU/APL from Cornell University , spent last summer as a SUIA researcher in the (Theme 3) labs of Drs. Nuth, Dworkin, and Johnson at NASA/GSFC.


Becker L et al. (1997) Geochim. Cosmochim. Acta 61 , 475-481.

Elsila JE et al. (2004) Anal. Chem. 76 , 2430-2437.

Kissin YV (2003) Geochim. Cosmochim. Acta 67 , 1723-1735.

Plows FL et al. (2003) Geochim. Cosmochim. Acta 67 , 1429-1436.

    William Brinckerhoff William Brinckerhoff
    Objective 3.1
    Sources of prebiotic materials and catalysts

    Objective 7.1
    Biosignatures to be sought in Solar System materials