• Has Cassini found a universal driver for prebiotic chemistry at Titan?

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    http://m.esa.int/Our_Activities/Space_Science/Cassini-Huygens/Has_Cassini_found_a_universal_driver_for_prebiotic_chemistry_at_Titan

    Has Cassini found a universal driver for prebiotic chemistry at Titan?
    European Space Agency
    July 26, 2017

    The international Cassini-Huygens mission has made a surprising detection
    of a molecule that is instrumental in the production of complex organics within the hazy atmosphere of Saturn's moon Titan.

    Titan boasts a thick nitrogen and methane atmosphere with some of the
    most complex chemistry seen in the Solar System. It is even thought to
    mimic the atmosphere of early Earth, before the build-up of oxygen. As
    such, Titan can be seen as a planet-scale laboratory that can be studied
    to understand the chemical reactions that may have led to life on Earth,
    and that could be occurring on planets around other stars.

    In Titan's upper atmosphere, nitrogen and methane are exposed to
    energy from sunlight and energetic particles in Saturn's magnetosphere.
    These energy sources drive reactions involving nitrogen, hydrogen and
    carbon, which lead to more complicated prebiotic compounds.

    These large molecules drift down towards the lower atmosphere, forming
    a thick haze of organic aerosols, and are thought to eventually reach
    the surface. But the process by which simple molecules in the upper atmosphere are transformed into the complex organic haze at lower altitudes is complicated

    and difficult to determine.

    One surprising outcome of the Cassini mission was the discovery of a particular

    type of negatively charged molecule at Titan. Negatively charged species
    - or "anions" - were not something scientists expected to find, because they are highly reactive and should not last long in Titan's atmosphere before combining with other materials. Their detection is completely reshaping current understanding of the hazy moon's atmosphere.

    In a new study published in Astrophysical Journal Letters, scientists identified some of the negatively charged species as what are known as
    "carbon chain anions". These linear molecules are understood
    to be building blocks towards more complex molecules, and may have acted
    as the basis for the earliest forms of life on Earth.

    The detections were made using Cassini's plasma spectrometer, called
    CAPS, as Cassini flew through Titan's upper atmosphere, 950-1300
    km above the surface. Interestingly, the data showed that the carbon chains became depleted closer to the moon, while precursors to larger aerosol molecules underwent rapid growth, suggesting a close relationship between
    the two, with the chains "seeding" the larger molecules.

    "We have made the first unambiguous identification of carbon chain
    anions in a planet-like atmosphere, which we believe are a vital stepping-stone

    in the production line of growing bigger, and more complex organic molecules, such as the moon\u2019s large haze particles," says Ravi Desai of
    University College London and lead author of the study.

    "This is a known process in the interstellar medium, but now we've
    seen it in a completely different environment, meaning it could represent
    a universal process for producing complex organic molecules.

    "The question is, could it also be happening within other nitrogen-methane atmospheres like at Pluto or Triton, or at exoplanets with similar properties?"

    "The prospect of a universal pathway towards the ingredients for
    life has implications for what we should look for in the search for life
    in the Universe," says co-author Andrew Coates, also from UCL, and co-investigator of CAPS.

    "Titan presents a local example of exciting and exotic chemistry,
    from which we have much to learn."

    Cassini's 13-year odyssey in the Saturnian system will soon draw
    to a close, but future missions, such as the international James Webb
    Space Telescope and ESA's Plato exoplanet mission are being equipped
    to look for this process not only in our own Solar System but elsewhere. Advanced ground-based facilities such as ALMA could also enable follow-up observations of this process at work in Titan's atmosphere, from
    Earth.

    "These inspiring results from Cassini show the importance of tracing
    the journey from small to large chemical species in order to understand
    how complex organic molecules are produced in an early Earth-like atmosphere," adds Nicolas Altobelli, ESA's Cassini-Huygens project scientist.

    "While we haven't detected life itself, finding complex organics
    not just at Titan, but also in comets and throughout the interstellar
    medium, we are certainly coming close to finding its precursors."

    Notes for Editors

    "Carbon chain anions and the growth of complex organic molecules
    in Titan\'s ionosphere," by R. T. Desai et al is published in
    Astrophysical Journal Letters.

    Cassini-Huygens is a cooperative project of NASA, ESA and ASI, the
    Italian space agency.

    For further information, please contact:

    Ravi Desai
    Mullard Space Science Laboratory, University College London
    Email: r.t.desai@ucl.ac.uk

    Andrew Coates
    Mullard Space Science Laboratory, University College London
    Email: a.coates@ucl.ac.uk

    Nicolas Altobelli
    ESA Cassini-Huygens Project Scientist
    Tel: +34 91 813 1201
    Email: nicolas.altobelli@esa.int

    Markus Bauer
    ESA Science Communication Officer
    Tel: +31 71 565 6799
    Mob: +31 61 594 3 954
    Email: markus.bauer@esa.int

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