The Chemistry and Physics of Titan's Upper Atmosphere Revealed by the Atacama Large Millimeter/submillimeter Array

Catholic University Of America, Washington DC

Investigators

Abstract

The atmosphere of Saturn's moon Titan is composed of molecules such as nitrogen and carbon and other elements that were present in the early atmospheres of the rocky planets like Earth. We study Titan's atmosphere to learn more about the early history of the Earth's atmosphere. Cassini spacecraft has mapped simple carbon and nitrogen molecules, revealing many patterns of molecules that change with the changing seasons of Titan. These are, however, only a small number of the types of molecules in Titan's atmosphere, and we do not have coverage of the atmosphere across all of Titan. This is Cassini's last year of operation. Using the new Atacama Large Millimeter/submillimeter Array (ALMA) radio telescope observatory at the same time as Cassini, the astronomers will observe Titan's atmosphere completely using both the radio telescopes and the spacecraft. They will make the first 3-dimensional maps of the types and amounts of molecules in Titan's atmosphere. They will then model the results to learn about how the molecules in the atmosphere are produced, transported, and changed with time. Undergraduate physics and astronomy students from minority-serving schools in the Washington DC area will conduct independent Solar System research with the principal investigator's input and backing at NASA's Goddard Space Flight Center. Saturn's moon Titan has a thick nitrogen and carbon-rich atmosphere, abundant in complex organic molecules. It is a potential analogue for primitive terrestrial bodies (including the early Earth). Instruments onboard NASA's Cassini spacecraft have provided maps of the smaller hydrocarbons and nitriles, revealing many complex, seasonally-varying molecular abundance patterns. These observations, however, trace only a small subset of Titan's molecular inventory, and have incomplete spatial and temporal coverage. Understanding the formation and evolution of Titan's atmospheric gases is a key step in determining the molecular inventories present in other primitive planetary atmospheres. The Atacama Large Millimeter/submillimeter Array (ALMA) is a revolutionary tool for the detection and instantaneous daylight-hemisphere mapping of Titan's gases. ALMA will be used concurrently with Cassini during its final year of operation to provide complete views of Titan's atmosphere. This research will produce the first instantaneous, spatially-resolved 3-dimensional molecular abundance maps for multiple molecular species on Titan, allowing new and rigorous tests for understanding the basic physics and chemistry of planetary atmospheres. Interpretation of these maps will help generate more detailed chemical models to provide insight into the global production, transport and evolution of molecular material, particularly in Titan's less well-studied middle and upper atmospheres. Isotope abundance ratios will help constrain chemical pathways and trace the origin and evolution of Titan's hydrogen and nitrogen. The principal investigator will mentor undergraduate physics and astronomy students from minority-serving institutions in the Washington DC area, who will conduct independent Solar System research at NASA's Goddard Space Flight Center.