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2012 Annual Science Report

NASA Goddard Space Flight Center Reporting  |  SEP 2011 – AUG 2012

Research Activities in the Astrobiology Analytical Laboratory

Project Summary

We are a laboratory dedicated to the study of organic compounds derived from past and future sample return missions, meteorites, lab simulations of Mars, interstellar, proto-planetary, and cometary ices and grains, and instrument development. This year, we continued our analyses of amino acids in carbonaceous chondrites, identifying large L-enantiomeric excesses in the Tagish Lake meteorite that may point towards abiotic processes that could lead to homochirality. We made the first detection of amino acids in CH and CB chondrites, and used compound-specific isotopic analysis to understand formation mechanisms for amino acids in CM and CR chondrites. We hosted two graduate students, welcomed a new NAI NPP postdoctoral researcher to our laboratory, and participated in numerous public outreach and education events, including providing a lecturer to the annual NAI Santander Summer School. We continued our participation in the OSIRIS-REx asteroid sample return mission and provided support for the Sample Analysis at Mars instrument of NASA’s Mars rover Curiosity.

4 Institutions
3 Teams
7 Publications
0 Field Sites
Field Sites

Project Progress

We are a laboratory dedicated to the study of organic compounds derived from past and future sample return missions, meteorites, lab simulations of Mars, interstellar, proto-planetary, and cometary ices and grains, and instrument development. We focus on relatively unprocessed materials, such as those from comets and asteroids, that are remnants of the early solar system and can shed light on the formation and evolution of the chemical nature of our solar system. In addition to studying authentic extraterrestrial materials such as meteorites and interplanetary dust particles, we work with other labs within GCA and other NAI teams that can simulate relevant extraterrestrial environments and chemistry.

The Astrobiology Analytical Laboratory employs commercial analytical instruments, configuring and optimizing them for small organic molecules of astrobiological interest. We also use our commercial instruments to assist in designing and testing flight instruments for future planetary missions. To further the study of authentic samples, extraterrestrial samples, and their analogs, this year we achieved the following:

*We identified large (~43 to 59%) L-enantiomeric excesses of aspartic and glutamic acid in fragments of the Tagish Lake carbonaceous chondrite (Figure 1). This work built on our previous work with a Canadian-led consortium, in which we reported on differences in amino acid abundances that correlated with aqueous alteration in three fragments of this meteorite. Carbon isotopic measurements indicated that the aspartic acid enantioenrichment is indigenous to the meteorite, and not the result of terrestrial contamination. The results can be explained by solid-solution phase behavior of these amino acids. The detection of nonterrestrial L-proteinogenic amino acid excesses in the Tagish Lake meteorite provides support for the hypothesis that significant enantiomeric enrichments for some amino acids could form by abiotic processes prior to the emergence of life. We published this result in Meteoritics and Planetary Science (Glavin et al., 2012) and issued a press release which received moderate media attention. This work was also supported by the NASA Cosmochemistry Program.

Figure 1. Extracts of the Tagish lake meteorite contain an excess of the L-enantiomer of aspartic acid over the D-enantiomer, while the amino acid alanine is found as a racemic mixture (L-enantiomer = D-enantiomer). Carbon isotopic measurements rule out terrestrial contamination and indicate that this L-excess is indigenous to the meteorite. Solution-solid phase interactions may account for this L-excess, which supports the hypothesis that significant enantiomeric excesses for some amino acids could from abiotically and help lead to the homochirality essential to life.

*We examined six carbonaceous chondrites from the metal-rich CH and CB classes that had not previously been investigated for amino acids. We made the first reported discovery of amino acids in these meteorites, using carbon isotopic measurements to support their extraterrestrial origin. Extracts of CH chondrites were found to be particularly rich in amino acids while CB chondrite extracts had much lower abundances. The amino acid distributions of the CH and CB chondrites were distinct from the distributions observed in type 2 and 3 CM and CR chondrites (Figure 2), providing evidence that multiple amino acid formation mechanisms were important in CH and CB chondrites. This work is currently in review in Meteoritics and Planetary Science (Burton et al., in review). This work was also supported by the NASA Cosmochemistry Program.

Figure 2. Structural distributions of the five-carbon amino acids in extracts from carbonaceous chondrites spanning a range of petrographic classes, thermal alteration, and aqueous alteration normalized to the total number of possible structural isomers. The dashed line corresponds to the expected relative abundance if the amino acids were formed by a completely non-selective synthetic process. In most cases there is structural similarity in C5 amino acid relative abundances within a single meteorite group; however, between meteorite groups a great deal of variability is observed, suggesting a variety of formation mechanisms. From Burton et al., in review.

*We completed a study of carbon, hydrogen, and nitrogen compound-specific isotopic ratios of amino acids in seven CR and CM carbonaceous chondrites, and used these measurements to identify potential formation environments and mechanisms for the compounds. We published this work in Meteoritics and Planetary Science (Elsila et al., 2012). This work was also supported by the NASA Cosmochemistry Program.

*We analyzed eight CM2 carbonaceous chondrites for nicotinic acid (a molecule involved in modern metabolism) and its structural isomers in three different extracts (hot water-unhydrolyzed, hot water-acid hydrolyzed, and formic acid) by liquid chromatography coupled to UV detection and high resolution Orbitrap mass spectrometry. We measured abundant nicotinic, isonicotinic, and picolinic acid in CM2s, which suggested that this particular group of carbonaceous chondrites likely delivered these important molecules to the early Earth. The manuscript for this research is currently in preparation and will be submitted to the journal Meteoritics and Planetary Science (Smith K. E., Callahan M. P., Burton A. S., Dworkin J. P., Gerakines P. A., Hudson R. L. and House C. H., The analysis of metabolic precursors in CM2 type carbonaceous chondrites).

*We analyzed five martian SNC meteorites for amino acids and nucleobases by liquid chromatography-mass spectrometry. We did not detect nucleobases above our detection limits in formic acid extracts; however, we did measure a suite of protein and non-protein amino acids in acid-hydrolyzed hot water extracts. To our knowledge, this research represented the first search for nucleobases in martian meteorites, the first amino acid analysis of Roberts Massif 04262, and the first compound-specific isotopic measurements for amino acids in martian meteorites. This research was also supported by the NASA Cosmochemistry program (PI: Callahan). Our results will be submitted to the journal Meteoritics & Planetary Science very soon (Callahan, M. P., Burton, A. S., Elsila, J. E., Baker, E. M., Smith, K. E., Glavin, D. P. and Dworkin, J. P., A search for amino acids and nucleobases in martian meteorites using liquid chromatography-mass spectrometry).

*We participated in a consortium to analyze fragments of the Sutter’s Mill meteorite, a carbonaceous chondrite that fell in California in April, 2012. We used our optimized analytical techniques to examine the amino acid content and bulk carbon and nitrogen isotopic ratios for three fragments. The consortium’s work is in press in Science (Jenniskens et al., in press).

*We hosted two graduate students from NAI teams at other institutions. The first, Karen Smith from Penn State, continued her work in our lab examining nitrogen heterocyclic molecules in spark-discharge experiments and in meteorites as part of her Ph. D. dissertation. The second, Eric Parker from Georgia Institute of Technology, spent a summer examining cyanamide spark-discharge samples and learning meteoritic amino acid analysis methods through a NASA Planetary Biology Internship.

*We also hosted two high school students: Eleni Baker, from Bullis School, Potomac, MD, who assisted in the martian meteorite analyses, and Sarah Grunsfeld, from River Hill High School in Clarksville, MD, who is assisting in studies of amino acid crystallizations and enantiomeric excesses.

*We welcomed a new NAI NPP postdoctoral fellow, Jose Aponte, into our laboratory in August, 2012, to work on new methods for detection of organic compounds in meteorites and other samples.

*We completed publication of a third paper (in Origins of Life and Evolution of Biospheres, Parker et al., 2011) with the NAI team at the Carnegie Institution of Washington and other co-authors on examinations from some of Stanley Miller’s original spark discharge experiments.

*Dworkin continued to serve as Project Scientist for the OSIRIS-REx New Frontiers-3 asteroid sample return mission. Glavin is a Co-I, while Elsila and Callahan are Collaborators. The Astrobiology Analytical Lab is heavily involved in this mission, both in the Contamination Control and Contamination Knowledge areas and in the eventual analysis of returned asteroidal material. This mission addresses three points of the Astrobiology Roadmap: Determining any chemical precursors of life in the solar system; Characterizing the cosmic sources of matter for potentially habitable environments in the solar system; and Understanding the principles that will shape the future of life, both on Earth and beyond.

*We supported the Mars Sample Laboratory’s Sample Analysis at Mars (SAM) instrument by performing laboratory experiments on Mars simulants to better understand the potential for detection of organic compounds.