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Project Progress

A little over 4.5 billion years ago, our solar system was a disk of gas and dust, newly collapsed from a molecular cloud, surrounding a young and growing protostar. Today most of the gas and dust is in the spectacularly diverse planets and satellites of our solar system, and in the Sun. How did the present state of the planetary system come to be from such undistinguished beginnings? The telling of that story is an exercise in forensic science. The “crime” occurred a long time ago and the “evidence” has been tampered with, as most planets and satellites display a rich variety of geological evolution over solar system history.

Fortunately, not all material has been heavily processed. Comets and asteroids represent largely unprocessed material remnant from the early solar system and they are represented on Earth by meteorites and interplanetary dust particles. Furthermore, telescopic studies of the birthplaces of other solar systems allow researchers to simulate those environments in the laboratory so that we may characterize the organic material produced.

We are a laboratory dedicated to the study of organic compounds derived from Stardust and future sample return missions, meteorites, lab simulations of Mars, interstellar, proto-planetary, and cometary ices and grains, and instrument development. Like forensic crime shows, the Astrobiology Analytical Laboratory employs commercial analytical instruments. However, ours are configured and optimized for small organic molecules of astrobiological interest instead of blood, clothing, etc. This role allows us to work with other themes within GCA and other NAI teams. To further the study of authentic samples, extraterrestrial samples, and their analogs, this year we achieved the following:

• We conclusively demonstrated the presence of indigenous nucleobases and other purines in carbonaceous chondrites, resolving a 50-year-old debate. We examined 11 carbonaceous chondrites and one ureilite and discovered a diverse suite of nucleobases, including three unusual and terrestrially rare nucleobases (Figure 1). In a parallel experiment, we found an identical suite of nucleobases and nucleobase analogs generated in reactions of ammonium cyanide. This work was published in Proceedings of the National Academy of Sciences (PNAS) and received widespread media attention.

• We examined 13 thermally altered meteorites and made the first reported discovery of indigenous amino acids in CV and CO chondrites. Our results showed a distinctly different distribution of amino acids in these thermally altered meteorites compared to previously studied, aqueously altered meteorites (Figure 2). The results of this work were submitted for publication in Meteoritics & Planetary Science.

• We expanded our search for amino acid enantiomeric excesses to include the more aqueously altered CM1 and CR1 meteorites. This work provides additional evidence that amplification of left-handed amino acid enantiomeric excesses occurred on the meteorite parent body during an extended aqueous alteration phase. A manuscript based on this work was published in Meteoritics and Planetary Science.
• With colleagues at the University of Alberta and the NAI team at the Carnegie Institution of Washington, we studied the amino acid distribution and stable isotopes in three unusual and pristine samples of the Tagish Lake meteorite. Results of this work were published in Science.
• With the NAI team at the Carnegie Institution of Washington, we studied the amino acids in extracts from some of Stanley Miller’s original spark discharge experiments, including those containing sulfur. This work has led to three publications (one in Proceedings of the National Academy of Sciences, two in Origins of Life and Evolution of Biospheres).
• We performed the first amino acid analysis of the meteorite Almahata Sitta, aka asteroid 2008 TC3. A manuscript was published in Meteoritics and Planetary Science. We followed up this work with the study of the thermally altered meteorites described above, which included more fragments of the Almahata Sitta meteorite.
• We finalized and published our measurements of the ¹³C and ¹⁵N enrichment in various amino acids in fungal peptides, in collaboration with Hans Brückner, Giessen University, Germany. We characterized the amino acids in these fungal peptides via LCMS. We showed that the isotopic ratio correlations as well as the chemical diversity and chirality are effective tools in distinguishing extraterrestrial origin from biological contamination. This work was published in Astrobiology.
• We continued to host one graduate student (Karen Smith, Penn State) who is examining nitrogen heterocyclic molecules in spark-discharge experiments and in meteorites as part of her Ph.D. dissertation.
• Dworkin and Glavin were deeply involved in the successful Phase A Proposal for the OSIRIS-REx New Frontiers-3 mission. Dworkin is Project Scientist for the mission, as well as lead for Contamination Control and Contamination Knowledge. The Astrobiology Analytical Laboratory will be heavily involved in this mission, both in the contamination studies and in the eventual analysis of returned asteroidal material. This carbonaceous asteroid sample return mission addresses three points of the Astrobiology Roadmap:

(2) Determine any chemical precursors of life in the solar system.
(3) Characterize the cosmic sources of matter for potentially habitable environments in the solar system.
(6) Understand the principles that will shape the future of life, both on Earth and beyond.