2012 Annual Science Report
NASA Ames Research Center Reporting | SEP 2011 – AUG 2012
Cosmic Distribution of Chemical Complexity
The three tasks of this project explore the connections between chemistry in space and the origin of life. We start by tracking the formation and evolution of chemical complexity in space, from simple carbon-rich molecules such as formaldehyde and acetylene to 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.
(1) 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 the photolysis of pyrimidine in astrophysical ices produces a host of new compounds, including the nucleobases uracil and cytosine (Figure 1).
Additional papers (completed and in process) describe the modeling of photolytic production of organics in the protosolar disk (Figure 2), and work done with the recently fallen Almahata Sitta and Sutter’s Mill meteorites.
(2) We substantially expanded content and capabilities of the PAH IR spectroscopic database (PAHdb) to support Spitzer, SOFIA, Herschel and JWST. A major highlight is the inclusion of the capability to directly import astronomical spectra and fit them with database spectra, providing deep new insight into the evolution of PAHs in different environments spanning the universe. We have routinely assisted users develop new PAHdb applications to PAH-related problems (PAHs in Titan, PAHs in Interstellar ices…). We are creating 2d-maps from Spitzer observations, showing UV-driven, spatial evolution of PAH subpopulations broken down by size, charge, composition, and we are relating these variations to changes in an object’s morphology, radiation field, PDR boundary, etc. (Figure 3).
We published four papers on the following topics: i – extension of spectra in PAHdb from C130H28 to C384H48 with astronomical applications, ii – long wavelength (15 – 20 µm) IR PAH emission based on spectra in PAHdb, iii – Analyzed spectral changes along 11 lines-of-sight in Orion PDR, tracking stepwise evolution of PAHs and fullerenes and iv – photochemistry of PAHs in NH3 and mixed H2O/NH3 ices (Figure 4).
(3) Mission involvement- Co-I Sandford continues contribute to the extraction, distribution, and analysis of cometary and interstellar samples returned by the Stardust mission. Several manuscripts that interpret several potential interstellar grains in the Stardust collection are almost ready for submission to the journals Science and Meteoritics and Planetary Science. He also continues to be actively involved with the study of asteroidal samples returned by the Japanese Hayabusa mission and publishing relevant papers (Figure 5).
Co-I Sandford is also 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 member of the Science Team 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 the first science results of SEVO have been published in a featured article in the journal Astrobiology. This paper discusses the chemical changes occurring in the PAH (isoviolanthrene) in a variety of astrobiological environments (see Figure 6) as well as the apparent stability of the quinone, anthrarufin against degradation. A second manuscript has been accepted for publication in Acta Astronautica. Several additional manuscripts that address the SEVO results and ground-control studies are in preparation.
PROJECT INVESTIGATORS:Louis Allamandola
PROJECT MEMBERS:Murthy Gudipati
RELATED OBJECTIVES:Objective 1.1
Formation and evolution of habitable planets.
Outer Solar System exploration
Sources of prebiotic materials and catalysts
Origins and evolution of functional biomolecules
Origins of cellularity and protobiological systems
Effects of extraterrestrial events upon the biosphere
Biosignatures to be sought in Solar System materials
Biosignatures to be sought in nearby planetary systems