Invited Presentation

Early results from the Large 12P COMA Survey - COmetary Molecules with ALMA

Author(s): Yi-Jehng Kuan (National Taiwan Normal University), Martin Cordiner (NASA Goddard Space Flight Center), and the COMA team

Presenter: Yi-Jehng Kuan (National Taiwan Normal University)

Cometary observations using the Atacama Large Millimeter/Submillimeter Array (ALMA) help elucidate the origin and composition of our Solar System's most ancient materials, and provide new insights into the physics and chemistry of cometary comae. In April-May 2024, the first ALMA Large Program for Solar System science was carried out (2023.1.01143.L: The Large 12P COMA survey (COmetary Molecules with ALMA) – PI: M. Cordiner). This program aimed to take advantage of the vast collecting area of the interferometer to perform comprehensive mm-wave spectral imaging of comet 12P (Pons-Brooks) — one of the brightest known periodic comets — on its first apparition in 71 years. The unprecedented sensitivity and high angular resolution of these data provide (1) the first ever spatial maps for multiple cometary gases, (2) isotopic ratios in key cosmogonic indicators (D/H, 14N/15N), (3) new insights into interstellar/protoplanetary disk ice compositions; and (4) tentative detections of new cometary molecules in the mm/sub-mm range. In this presentation, we provide an overview of the dataset, and some early results from our survey, including spectroscopic detections of at least 22 molecules, along with spectral/spatial maps and details on the coma physical/chemical/thermal structure. We will present the first ever maps of H2O and HDO in a Halley-type comet, and will discuss the D/H ratio with respect to the history of water in the Solar System.