2004 Annual Science Report
NASA Goddard Space Flight Center Reporting | JUL 2003 – JUN 2004
Investigation of the Evolution of Molecular Complexity in the Star-Forming Cores of Molecular Clouds
Research by the Blake group centers on an investigation of the evolution of molecular complexity in the star-forming cores of molecular clouds. Both laboratory and observational studies are carried out. This work began with an observational search for dihydroxyacetone (DHA), the simplest three carbon ketoses sugar. Over ten transitions have now been detected toward the galactic center source Sgr B2(N-LMH), a sample line is shown in the figure below. The top portion of the figure depicts the molecular structure and a portion of the laboratory spectrum assigned in our laboratory, while the bottom panel shows one of the DHA lines observed near 1.3mm toward Sgr B2(N-LMH). The rest velocities of the lines are nicely centered on that expected for complex molecules from detailed mapping with the Very Large Array, and a rotation diagram analysis of the integrated intensities yields excitation temperatures consistent with those of acetone and other organics. The column densities are also in line with chemical expectations from the earlier detections of chemically related compounds such as glycoaldehyde (the simplest, two carbon, sugar) and acetone.
Interestingly, searches by other groups for the three carbon aldose form, glyceraldehyde, have been unsuccessful. Thus, the chemistry that leads to such compounds must be structurally selective. This work is just beginning as part of the thesis work of Susanna Widicus; we plan to investigate the grain mantle and gas phase chemical networks responsible for chemical complexity in molecular clouds. These studies will be used to guide future searches with existing and soon-to-be-operational facilities.
Our detection of dihydroxyacetone shows that more complex species seen in carbonaceous chondrites can be detected in star-forming molecular cloud cores with new telescopes and arrays. We will work with Dr. Steve Charnley on theoretical models of such sources and with meteoriticists and laboratory experimentalists at NASA Goddard Space Flight Center (GSFC) to determine which additional organics to study spectroscopically in order to guide future observational searches with ground-based and space-born sensors.
PROJECT INVESTIGATORS:Geoffrey Blake
RELATED OBJECTIVES:Objective 3.1
Sources of prebiotic materials and catalysts