【TED-0621】There may be extraterrestrial life ...


来自: 我是什么垃圾?(暗黑城市上空的气态污染物) 2019-06-21 11:28:45

标题:【TED-0621】There may be extraterrestrial life in our solar system
  • 我是什么垃圾?

    我是什么垃圾? (暗黑城市上空的气态污染物) 2019-06-21 11:28:56

    Deep in our solar system,

    a new era of space exploration
    is unfolding.

    Beneath the thick ice of Europa,

    in the vapor plumes on Enceladus,

    and within the methane lakes of Titan,

    astrobiologists are on the hunt
    for extraterrestrial life.

    We’ve honed in on these three moons
    because each is an ‘ocean world,’

    an environment that contains
    a liquid ocean–

    and liquid can support
    the formation of life.

    Living organisms have to be able to grow,
    reproduce, and feed themselves,

    among other things.

    All of those functions require the
    formation of complex molecules

    from more basic components.

    Liquids such as water allow chemical
    compounds to remain in suspension

    instead of sinking under
    the force of gravity.

    This enables them to interact frequently
    in a 3-dimensional space and,

    in the right conditions,

    go through chemical reactions that
    lead to the formation of living matter.

    That alone isn’t enough;

    the small but complex biomolecules
    that we’re familiar with

    are sensitive to temperature—

    too hot or cold, and they won’t mix.

    Liquid water has an additional advantage

    in that it’s relatively

    meaning it can insulate molecules against
    large shifts in heat.

    On Earth, these and other conditions in
    aquatic environments

    may have supported the emergence
    of life billions of years ago.

    Tantalizingly, the same could be true
    in other parts of our solar system,

    like these three icy moons.

    Europa, which is a moon of Jupiter,

    is probably the most
    intriguing ocean world.

    Beneath a surface layer of ice thicker
    than Mount Everest,

    there exists a liquid ocean as much as
    100 kilometers deep.

    Astrobiologists think this hidden
    ocean could harbor life.

    Thanks to the Galileo probe,

    we can deduce that its
    potential salt content

    is similar to that of some lakes on Earth.

    But most of its characteristics will be a
    mystery until we can explore it further.

    Like Jupiter, Saturn also has moons that
    might have the right conditions for life.

    For instance– Enceladus is a tiny ball of
    ice that’s small enough to nestle

    within the surface area
    of the Gulf of Mexico.

    Similarly to Europa, it likely contains an
    ocean deep under the ice.

    But Enceladus also has geysers

    that frequently vent water vapor and
    tiny ice grains into space.

    Astrobiologists are curious about whether
    these geysers

    are connected to the ocean below.

    They hope to send a probe to test whether
    the geysers’ plumes of vapor

    contain life-enabling material
    from that hidden sea.

    Although it’s the best known substance
    for nurturing life,

    water isn’t necessarily the only medium
    that can support living things.

    Take Titan, Saturn’s largest moon,

    which has a thick nitrogen atmosphere

    containing methane and many other
    organic molecules.

    Its clouds condense and
    rain onto Titan’s surface,

    sustaining lakes and seas
    full of liquid methane.

    This compound’s particular chemistry means
    it’s not as supportive a medium as water.

    But, paired with the high quantities
    of organic material

    that also rain down from the sky,

    these bodies of liquid methane could
    possibly support unfamiliar life forms.

    So what might indicate that life exists on
    these or other worlds?

    If it is out there, astrobiologists
    speculate that it would be microscopic,

    comparable to the bacteria
    we have on earth.

    This would make it difficult to directly
    observe from a great distance,

    so astrobiologists seek clues
    called biosignatures.

    Those may be cells, fossils, or mineral
    traces left behind by living things.

    And finding any biosignatures will be
    challenging for many reasons.

    One of the biggest concerns

    is to make sure we sterilize our
    probes extremely thoroughly.

    Otherwise we could accidentally
    contaminate ocean worlds

    with Earth’s own bacteria,

    which could destroy alien life.

    Titan, Enceladus, and Europa

    are just three of possibly many
    ocean worlds that we could explore.

    We already know of several other
    candidates in our solar system,

    including Jupiter’s moons Callisto and

    Neptune’s Triton, and even Pluto.

    If there’s this much potential for life
    to exist in our own tiny solar system,

    what unimagined secrets might the
    rest of the universe contain?


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