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NASA’s Hubble Space Telescope
has directly imaged what may be

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plumes of water vapor on
Jupiter’s icy moon Europa.

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Europa has long been thought to
harbor a global ocean of water

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beneath its surface of ice,
making it a prime target of

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study for anyone interested in
searching for alien life.

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Eventually our search for life
will take us into that ocean,

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but until then, the existence of
a water vapor plume would

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provide an early glimpse into
the ocean’s conditions. In 2012,

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a team of astronomers used the
Hubble Space Telescope to

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observe a faint aurora from the
interaction of Europa and

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Jupiter’s magnetic field. They
detected emissions in

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wavelengths characteristic of
the breakup of water molecules,

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and after considering a wide
variety of causes, the team

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concluded that the most
plausible explanation for these

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spectroscopic measurements was
the existence of plumes of water

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vapor erupting from the surface
of Europa. Now a different team

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of astronomers has used a
different method with similar

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results - they used Hubble to
image Europa in ultraviolet

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light as the moon transited
across the disk of Jupiter and

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were actually able to take
direct images of what appear to

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be the silhouettes of plumes
rising about 125 miles above the

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surface of Europa. If these
observations are indeed of water

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vapor plumes, then they
approximately match the 2012

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observation estimates for the
plumes’ mass, height, and

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location. Also, these plumes are
transient, meaning they come and

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they go - out of ten
observations of Europa

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transiting across Jupiter, the
team saw possible plumes on just

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three of the transits. Both the
recent observations and the 2012

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observations provide evidence,
not proof, of water vapor plumes

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on Europa. Science is a process;
it’s not always cut-and-dried.

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But future observations by
Hubble, and infrared

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observations by the James Webb
Space Telescope, could continue

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to build a case for the
existence of these plumes on

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Europa. And then NASA’s future
Europa flyby mission would

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continue the search for the
plumes and visit them to look

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for evidence of a habitable
underwater world.

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[music ends]