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2013 Annual Science Report

NASA Ames Research Center Reporting  |  SEP 2012 – AUG 2013

Cosmic Distribution of Chemical Complexity

Project Summary

This project explores the connections between chemistry in space and the origin of life. It is comprised of three tightly interwoven tasks. We track the formation and evolution of chemical complexity in space starting with simple carbon-rich molecules such as formaldehyde and acetylene. We then move on to more complex species including amino acids, nucleic acids and polycyclic aromatic hydrocarbons. The work focuses on carbon-rich species that are interesting from a biogenic perspective and on understanding their possible roles in the origin of life on habitable worlds. We do this by measuring the spectra and chemistry of analog materials in the laboratory, by remote sensing with small spacecraft, and by analysis of extraterrestrial samples returned by spacecraft or that fall to Earth as meteorites. We then use these results to interpret astronomical observations made with ground-based and orbiting telescopes.

4 Institutions
3 Teams
11 Publications
1 Field Site
Field Sites

Project Progress

We have published several papers, and are working on others, that describe the production of prebiotic compounds by UV irradiation of cosmic ices. One of the published papers appeared in Astrobiology and described work showing that the photolysis of pyrimidine in astrophysical ices produces a host of new compounds, including all of the pyrimidine-based nucleobases, including cytosine (Figure 1).

Figure 1. UV photolysis of pyrimidine in mixed molecular ices leads to the formation of all three of the pyrimidine-based nucleobases - uracil, cytosine, and thymine (Materese et al. 2013).

Additional papers describe organic nanoglobules found in carbonaceous meteorites (Figure 2) (published in Meteoritics and Planetary Science) and studies done with the recently fallen Sutter’s Mill meteorite (paper currently slated for publication in a special issue of Meteoritics and Planetary Science that will be devoted to this meteorite).

Figure 2. Primitive carbonaceous chondrites contain enigmatic organic nanoglobules that often contain isotopic anomalies in D and 15N that indicate an interstellar or protosolar origin (De Gregorio et al. 2013).

We have published two papers that resulted in two press releases, and submitted two manuscripts. The first paper analyzes Spitzer spectral data cubes on the reflection nebula, NGC 7023, exclusively using polycyclic aromatic hydrocarbon (PAH) spectra and tools in the PAH database (PAHdb) generated in the Ames Astrochemistry Laboratory. 2D-maps of the region show, for the first time, UV-driven, spatial evolution of PAH subpopulations broken down by size, charge (Figure 3), and composition, variations that probe subtle changes in the morphology, radiation field, photodissociation region (PDR) boundary, etc. This work marks a number of 'firsts.’

Figure 3. Northwest PDR in Reflection Nebula NGC 7023. Left: Fraction of total PAH surface brightness from neutral PAHs. Right: Fraction of total PAH surface brightness from PAH cations. The PAH breakdown maps were made by blind algorithm-driven-machine analyses of 300 spectra using PAHdb.

The second paper also marks a number of 'firsts’ and illustrates the global interest for PAHdb (Figure 4). It represents an unusual application to data returned by the Cassini spacecraft; it reports the presence of PAHs in the atmosphere of Saturn’s largest moon, Titan. Finally, the content and capabilities of PAHdb have been substantially expanded and will be made publicly available by the end of 2013 in a version 2.00 release, timed to coincide with a coupled publication.

Figure 4. Global reach of NASA Ames PAH IR spectroscopic database (PAHdb). Map of the world showing places of origin for visitors that have geographical information associated with their IP-address. Data as of September 6, 2013.

Mission involvement- Co-I Sandford continues to be involved with extraction, distribution, and analysis of cometary and interstellar samples returned by the Stardust mission. A host of papers (11) describing several potential interstellar grains in the Stardust collection have been accepted for publication Meteoritics and Planetary Science and they will appear simultaneously with an overview paper in Science. Dr. Sandford also continues to be actively involved as a member of the OSIRIS-Rex Asteroid Sample Return Mission, where he will have numerous responsibilities, including organizing the science team that will study the organics in the returned samples. Finally, Co-I Sandford is currently serving as the PI on a Comet Surface Sample Return mission concept for the next New Frontiers AO. Co-I Andrew Mattioda is a Senior Science Team member for the O/OREOS (Organisms/ORganics Exposure to Orbital Stresses), NASA’s first Astrobiology Small Payloads mission, which launched on November 19, 2010. He works on the SEVO (Space Environment Viability of Organics) component of O/OREOS. Numerous talks have been given and two SEVO science results papers have been published discussing the science results and ground control experiments. One paper discusses the chemical changes occurring in the Iron Tetraphenylporphyrin Chloride in a variety of astrobiological environments (see Figure 6) as well as the apparent stability of the quinone, anthrarufin to degradation. The second paper discusses the technical aspects of setting up ground controls to mimic space flight conditions. This paper has been accepted for publication in the Astrophysical Journal Supplements. Co-I Mattioda is also involved in OREOCube, which involves collaboration with the European Space Agency to place two UV-Vis spectrometers and organic samples on an external science platform on the International Space Station (ISS). This experiment, slated to launch in 2015, will monitor the chemical evolution of various organic and inorganic thin films under astrobiologically relevant conditions.

Figure 5. (a)-(c) UV/VIS spectra of samples exposed to radiation in low-Earth orbit aboard SEVO, obtained in situ using the Sun as the spectroscopy light source. The bottom traces in each panel were taken before flight with a laboratory spectrometer and light source. Duplicate Humid and Atmosphere sample cells underwent spectral changes similar to those shown here. Indicated exposure times are actual time of Sun exposure, corrected for the rotation of the satellite in and out of sunlight and for periods of solar eclipse. (d)-(f) UV/VIS spectra of samples in the laboratory irradiation experiment. The bottom traces in each panel were taken before irradiation. Laboratory samples were exposed to a Xe full-spectrum (AM0) solar simulator combined with a H2-He discharge lamp matched to solar Lyman-α intensity in low-Earth orbit. The duplicate Atmosphere cell underwent spectral changes similar to the one shown here. Indicated exposure times are actual time of solar simulator exposure, corrected for the rotation of the samples in and out of the beam. The vertical dotted lines indicate the positions of the Bx Soret band component. The vertical dashed and solid lines indicate the positions of the By Soret component for the Humid and Inert Atmosphere cells, respectively.

    Louis Allamandola Louis Allamandola
    Project Investigator
    Christiaan Boersma

    Amanda Cook

    Murthy Gudipati

    Christopher Materese

    Andrew Mattioda

    Michel Nuevo

    Scott Sandford

    Max Bernstein

    Jan Cami

    Jamie Cook

    Jason Dworkin

    Els Peeters

    Objective 2.1
    Mars exploration.

    Objective 2.2
    Outer Solar System exploration

    Objective 3.1
    Sources of prebiotic materials and catalysts

    Objective 3.2
    Origins and evolution of functional biomolecules

    Objective 3.4
    Origins of cellularity and protobiological systems

    Objective 4.3
    Effects of extraterrestrial events upon the biosphere

    Objective 7.1
    Biosignatures to be sought in Solar System materials

    Objective 7.2
    Biosignatures to be sought in nearby planetary systems