2012 Annual Science Report
University of Hawaii, Manoa Reporting | SEP 2011 – AUG 2012
Ice Chemistry of the Solar System
We are currently in the process of establishing a research program at the University of Hawai’i at Manoa to investigate the evolution of Solar System and interstellar ices; these grains are chemically processed continuously by radiation from either our Sun, or galactic cosmic radiation (GCR). The nature of the chemistry that occurs here is an important component of understanding the origin of complex biomolecules that could have seeded the primordial Earth, helping to kick-start the origin of life. We have constructed one of the leading laboratory facilities in the world capable of carrying out this research, and we focus on establishing the underlying chemical pathways.
We have conducted experiments on the effects of energetic electrons on ice mixtures of carbon dioxide (CO2) and chlorine (Cl2) ices in an attempt to understand the potential origin of perchlorate (ClO4) found on both Earth and Mars. We studied the products formed through both Fourier Transform Infrared spectroscopy (FTIR) and quadruple mass spectrometry (QMS) and thus identified the formation of several key chlorine oxides (ClxOy). We are now working with collaborator Sushil K. Atreya to help incorporate our results into chemical models.
Recent results from the W.M. Keck Research Laboratory in astrochemistry include the formation of high molecular weight hydrocarbons upon interaction with ionizing radiation starting from pure, simple saturated hydrocarbon ices such as methane (CH4), ethane (C2H6), propane (C3H8), and n-butane (C4H10). The species are detected – in addition to FTIR, Raman, and UV-Visible spectroscopy – using a novel application of reflection time-of-flight (ReTOF) mass spectrometry coupled with soft vacuum ultraviolet photoionization at 10.5 eV. In particular, results from ReTOF spectroscopy with soft vacuum ultraviolet photoionization of the subliming products of processed methane ice indicate that over 50 molecules with distinct m/z ratios and sublimation temperatures are formed easily under conditions relevant astrophysical environments. Despite, the numerous previous experimental investigations probing the effect of ionizing radiation on simple hydrocarbon astrophysical ice analogs, our results suggest that there is still a vast unknown molecular composition synthesized upon exposure of these ices to ionizing radiation.
Since water-bearing sulfates have been identified on the Martian surface and implicated on Jupiter’s moons Europa and Ganymede, we have begun studying the specific hydration states of these minerals by a technique that could be used in real space missions to identify these species. Raman spectroscopy is ideally suited to this purpose, since the degree of hydrogenation of each species gives a unique Raman fingerprint. Here, we have developed a novel instrument to study the degree of hydration of minerals in situ by combining an acoustic levitator, pressure compatible process chamber, and Raman spectroscopy capable of working under daylight conditions. Minerals studied so far include magnesium sulfate (MgSO4 ∙ nH2O; n = 7, 6, . . ., 0), gypsum (CaSO4 ∙ 2H2O), bassanite (CaSO4 ∙ 0.5H2O), and anhydrite (CaSO4).
Finally, we have found conclusive evidence on the formation of two proteinogenic dipeptides-Gly–Gly and Leu–Ala-formed via electron-irradiation of interstellar model ices followed by annealing the irradiated samples to 300 K. Our results indicate that the radiation-induced, non-enzymatic formation of proteinogenic dipeptides in interstellar ice analogs is possibility. Furthermore, once synthesized and incorporated into the “building material” of solar systems, biomolecules at least as complex as dipeptides could have been delivered to habitable planets such as early Earth by meteorites and comets, thus seeding the necessary components for life as we know it.
PROJECT MEMBERS:Chris Bennett
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 energy transduction
Earth's early biosphere.
Biosignatures to be sought in Solar System materials
Biosignatures to be sought in nearby planetary systems