The nucleus of comet 67P Churyumov-Gerasimenko (“Chury”) as seen by the European Rosetta space probe.
Credit: © ESA / Rosetta / MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
The ESA’s Rosetta mission, which ended in September 2016, found that organic matter made up 40% (by mass) of the nucleus of comet 67P Churyumov-Gerasimenko, a.k.a. Chury. Organic compounds, combining carbon, hydrogen, nitrogen, and oxygen, are building blocks of life on Earth. Yet, according to Jean-Loup Bertaux and Rosine Lallement — from the Laboratoire Atmosphères, Milieux, Observations Spatiales (CNRS / UPMC / Université de Versailles Saint-Quentin-en-Yvelines) and the Galaxies, Étoiles, Physique et Instrumentation department of the Paris Observatory (Observatoire de Paris / CNRS / Université Paris Diderot), respectively — these organic molecules were produced in interstellar space, well before the formation of the Solar System. Bertaux and Lallement further assert that astronomers are already familiar with much of this matter.
Such primitive nebulae end up contracting to form a solar system like our own, with planets . . . and comets. The Rosetta mission taught us that comet nuclei form by gentle accretion of grains progressively greater in size. First, small particles stick together into larger grains. These in turn combine into larger chunks, and so on, until they form a comet nucleus a few kilometers wide.
Thus, the organic molecules that formerly populated the primitive nebulae — and that are responsible for DIBs — were probably not destroyed, but instead incorporated into the grains making up cometary nuclei. And there they have remained for 4.6 billion years. A sample-return mission would allow laboratory analysis of cometary organic material and finally reveal the identity of the mysterious interstellar matter underlying observed absorption lines in stellar spectra.
If cometary organic molecules were indeed produced in interstellar space — and if they played a role in the emergence of life on our planet, as scientists believe today — might they not also have seeded life on many other planets of our galaxy?
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Story Source: Materials provided by University of Chicago Original written by Whitney Clavin.Note: Content may be edited for style and length.
Jean-Loup Bertaux, Rosine Lallement. Diffuse Interstellar Bands carriers and cometary organic material.. Monthly Notices of the Royal Astronomical Society, 2017; DOI: 10.1093/mnras/stx2231