Unusual Signal from Decades Ago Indicates the Presence of Hidden Oceans Orbiting Uranus
Around
Uranus, there might be some undiscovered seas.
One or more
of the gas giant's 27 known moons may contain liquid oceans beneath their
crusty ice and rock surfaces, according to new findings. Miranda and Ariel, one
or both of which may be erupting with ocean plumes, are the potential
perpetrators for seeding the space around Uranus with plasma.
The data,
which came from the Voyager 2 mission, the only spacecraft to have ever done so
and fly past the planet on its way to space nearly 40 years ago, provides a
compelling argument for sending another probe to Uranus.
Astronomer
Ian Cohen of the Johns Hopkins Applied Physics Laboratory says, "We've
been making this case for a few years now that energetic particle and
electromagnetic field measurements are important not just for understanding the
space environment but also for contributing to the larger planetary science
investigation.
It appears
that this is true even for material that predates me. It just goes to
demonstrate how beneficial it can be to visit a system and get a firsthand look
at it.
Charged
particles that looked to be trapped in particular areas of the Uranian
magnetosphere were detected by Voyager 2's Low-Energy Charged Particle
instrument during the spacecraft's 1986 flyby of Uranus. They should have
dispersed, but instead they stayed close to the equator, near Miranda's and
Ariel's paths.
At the time,
researchers thought the odd shape was a sign of an energetic electron injection
from a source like a substorm in Uranus' magnetic field. Cohen and his
associates discovered, however, that the electrons don't display the traits
anticipated of a substorm infusion upon closer inspection.
he
scientists were left starting from scratch in their quest to comprehend where
the electrons originated, which opened up a huge can of worms. The pitch angle
of the electrons, or the angle formed by their velocity vector and the magnetic
field, was said to be of special interest.
A steady
source of electrons would be needed to compensate for the scattering and loss
brought on by plasma waves in the planetary magnetosphere in order to maintain
the pitch angle recorded by Voyager 2.
The team
used modelling to predict that in the absence of a source of this kind, the
electron pitch angle distribution would become homogenous in a matter of hours
if it were in the right place and at the right angle.
The crew
searched the Voyager 2 data for such a source as they dug deeper. Their
simulations revealed a distinct and indisputable maximum in the area between
Miranda and Ariel, pointing to the possibility of an energetic ion source
there.
In the 37
years since Voyager 2 visited Uranus, scientists have made some progress in
figuring out what could be producing those ions. Similar signals were picked up
by Voyager 2 in the Saturnian orbit, and were subsequently determined by
Cassini to have come from the ocean moon Enceladus' icy geysers. We discovered
Europa, the oceanic moon of Jupiter, after another identical detection.
Cohen
asserts that energetic particle observations frequently precede the discovery
of an ocean world.
Miranda, the
smallest of Uranus' five major moons, or Ariel, the brightest, are the two
moons most likely to be involved at this time. It might be either. or either.
Both moons exhibit recent geologic resurfacing, which is compatible with the
eruption of liquid from within.
However, we
only have one sample at this time. The need for a dedicated mission to Uranus,
potentially with Neptune included, has grown among planetary scientists. There
are so many strange things about the world that learning more about them can
only be truly exciting and rewarding.
The
potential for wet moons is just the smelly cherry on top.
According to
Cohen, "the data are consistent with the extremely intriguing potential of
there being an active ocean moon there." "We can always model more
thoroughly, but the conclusion will always be limited until we have new
data."
Reference:
sciencealert.com
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