What do comets tell us about the origin of Earth?

Abstract: Comets are the most preserved remnants of the formation of the Solar system. At the time of birth of the planets, icy bodies provided material to build up the core of the giant planets. Later on they also seeded telluric planets with vast amounts of volatile materials and may have played a major role in supplying water to the young Earth. Following the migration of the giant planets the remaining icy bodies have constituted the two main cometary reservoirs: the Kuiper Belt and the Oort cloud. Among other techniques and in-situ exploration, submillimeter astronomy has been one of the most efficient technique to investigate the chemical and isotopic content of cometary atmospheres for the last 30 years. The abundance of over 25 molecular species and several isotopic ratios (D/H, 12C/13C, 14N/15N, 32S/34S,...) have been measured in comets via submm spectroscopy. ALMA has the potential of vastly increasing our knowledge of the chemical composition of comets (via the detection of a larger number of molecular species, measurements of isotopic ratios, or observations of more outstanding objects like, e.g., interstellar comet 2I/Borisov). Interferometry adds up the spatial resolution that helps to discriminate between molecular species that comes directly from the sublimation of nucleus ices and those created in the cometary atmospheres from degradation of grains or other sources to be characterized. I will show several examples of these recent achievements and the potential of ALMA in providing us with an in depth knowledge of these objects that are often qualified as the Rosetta stone of our Solar system.
Image credit: Katharina Immer/ALMA (ESO/NAOJ/NRAO)

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